Drastic Pygmy Cory Behavior Change

[Gemtrox42]

Hello, I noticed something interesting in my dwarf cory's behavior and wanted to know if anyone had any input. I have had my tank for about 7 months now, and for the first 3 months my dwarf corys were very active, constantly foraging on the bottom and swimming to the upper layers of the tank. Oftentimes they would swim up and down the glass in a similar manner to pacing, alone or in a shoal. Then late last year I had an ich infestation which claimed the lives of several of my fish, including 3 corys (not sure as I didnt see any white spots on them, but it was at the same time as the other fish). Since then I have replaced 2 of the corys, and the 5 of them are behaving radically differently. They now spend most of their time sedentary, staying under driftwood outcroppings and rarely move to the upper levels of the tank. The pacing-like behavior is completely gone, though some will still zip up for a bite of air. I haven't lost anymore since the ich, but the drastic change in behavior has got me super confused and a tad worried.

Background - I have a 30 gal tank with Current Satellite LEDs, lightly planted with gravel bottom, mostly hornwart, duckweed, swords and java ferns, lots of driftwood. My fish are 14 cardinals, 5 pygmy corys and 1 cherry shrimp, two adult mollies and around 2 dozen fry. Water is 80 degrees, hang on back filter so should be well oxygenated. Water parameters are 7.3 pH, ammonia 0, nitrites 0, nitrates 5, GH 75, KH 100-120. I am using softened wellwater. I treat the water with aquavitro seed, a dechlorinator, and seachem flourish, excel, and iron for my plants. Generally, my tank chemistry has been very stable over time, but I have noticed a slight trend towards higher GH (used to be ~50) and lower KH (used to be ~140). It may also be important to note that I did not start dosing my water with plant supplements until around the time I added the two new dwarf corys.

 

[UnknownFishies]

When did you add them. Might be they are just adjusting to the tank. Or maybe the die offs of the fish caused a disturbance in the pecking order.

 

[Byron]

You are right to be concerned over the described change, it is a sign of weakening fish, especially in Corydoradinae species. There are a few problems that I will say with certainty will affect the cories--and some of these issues the other fish in time. I will do my best to explain.

First, the substrate. Sand is essential for cories, and especially the three "dwarf" species. [BTW, is the species Corydoras pygmaeus, or one of the other two (C. habrosus, C. hastatus)? Worth knowing, though what follows applies to all regardless.] I don't know what "gravel" may refer to here, but anything larger in grain size than very fine river gravel is long-term a problem because anything that adds stress to a fish can exacerbate any other problem. All Corydoradinae species are technically/scientifically termed "filter feeders," and this is an instinct programmed into the fish's DNA and thus important. Smoothness of the substrate is another factor but even if smooth gravel is still problematic; for one thing, bits of food more easily get down where the fish cannot reach it, causing increased bacterial issues for substrate fish. We can move on to the much more critical issues, but keep a change to sand (or another tank with sand for the cories) in mind, and question me later on pursuing this issue if you like.

Water parameters. Temperature at 80F is way too warm for any cories on a permanent basis, and again especially problematic for the dwarf species. [Another brief aside--small sized fish have higher metabolisms, which means they work harder to maintain necessary physiological functioning, and so detriments have more impact too. And as the temperature directly drives the metabolism of each fish, this can be a serious issue.] The temp should be down around 75/76F, absolutely no higher for the cories on a permanent basis (increasing heat to deal with something like ich is temporary). The lower temp will not harm the other named fish, at least no where near as much as the cories.

Another aside (sorry)--don't know how you dealt with the ich, but most soft water species are much more sensitive to many medications, and cories are in this group. Heat, with salt sometimes, is far safer.

The other parameters (GH, KH, pH) are OK for the cories (and cardinals) but are frankly a slow death knell for the two mollies. This fish must have moderately hard or harder water (it cannot be too hard, realistically (GH minimum 12dGH (214 ppm or mg/l) up to 30 dGH (537 ppm or mg/l); the cories and cardinals will not benefit from this though. Straight well water might be best for the mollies depending upon the GH/KH/pH of your well water on its own; I'll move on to the next issue as the GH is not the cory problem, but the additives to achieve it may be.

Re softening the water. Can you explain how you are achieving this? None of the mentioned additives will impact GH/KH, and the comment that the GH is slowly increasing is reason enough to sort out why. Parameters in any fish tank should be quite stable over days, months, even years; this applies to GH, pH and even nitrate [which is not a parameter but a condition and another topic].

I know nothing about aquavitro seed, but the info on their site reads "rapidly and safely establish the aquarium biofilter; synergistic blend of aerobic, anaerobic, and facultative bacteria." This sounds like a nitrifying bacteria supplement of some sort, and if so will not have any impact on GH. And once the aquarium is biologically cycled/balanced, should be unnecessary. Perhaps harmless in its own right, but any substance added to the water without good reason is best not added, as these do impact fish.

The plant additives are a concern. While these can sometimes aid the plants, depending upon the light (light intensity/spectrum alone is what drives photosynthesis, so nutrients just have to be sufficient for the plants' needs in balance with the light), they are still additives to the water and can impact fish, depending. Minimal is always better than excess, which usually means problem algae as well, but no matter; for the sake of all fish, minimal. Substrate tabs for larger rooted plants are a better option for this reason, though floaters and upper water plants obviously gain no benefit for substrate tabs. But it can be surprising how little additives may actually be necessary to keep things balanced. But there is one additive mentioned that is very dangerous, and that is Flourish Excell, and Flourish Iron can be deadly too.

"Flourish" I will assume means the Flourish Comprehensive Supplement for the Planted Aquarium, to give it its full name. I have been using this for years, but carefully. You might well find that Flourish Tabs inserted one next to each of the rooted sword plants, replaced every 3 months, will provide even better response than the liquid alone, it certainly has for me and I have zero GH water so no minerals there. FT do not release nutrients into the upper water column, hence they get to the plants in the substrate but not into the fish.

Iron should absolutely never be added alone, but only in a careful balance with all other required nutrients (there are 13 if memory serves me, all are in FC for a list except oxygen, hydrogen and carbon). Iron is often, or used to be, touted as the plant "cure" but it is only a micro-nutrient, and in FC it is in balance with the others so unnecessary. Iron is a heavy metal, deadly to all fish and plants in excess. And here again, what goes in the water is most likely diffusing across the fish cell membranes and entering the fish's bloodstream. Less is better.

Excell is certainly as bad if not worse. This is glutaraldehyde and water. This substance is used in embalming fluid, antifreeze, ship ballasts to kill bacteria--you get the idea. At bottle-recommended dose levels it usually kills Vallisneria and some other plants which should warn us of its dangers. If overdosed it can kill plants, fish and bacteria. The fact that it is reported to kill brush/beard algae is another warning sign. Nothing like this should ever go in a fish tank.

Which dechlorinator are you using? They are not all equal, believe me. Some contain toxic additives, some need more to work (= more in the water and more inside the fish). May have more when I know.

Hope this helps. And don't discourage, we all learned the above, and we want others to be successful, and not in time give up and leave the hobby as often occurs. I've been there too.

 

[mbsqw1d]

I am using softened wellwater.

Could be an issue, particularly with corydoras, if the method of softening water is by using resin that is 'charged' with sodium.
As the resin 'collects' calcium and magnesium, softening the water, they are exchanged for a small amount of sodium. This means that softened water contains a small amount of sodium, also known as salt to which corydoras are notoriously intolerant to.

 

[Gemtrox42]

You are right to be concerned over the described change, it is a sign of weakening fish, especially in Corydoradinae species. There are a few problems that I will say with certainty will affect the cories--and some of these issues the other fish in time. I will do my best to explain.

First, the substrate. Sand is essential for cories, and especially the three "dwarf" species. [BTW, is the species Corydoras pygmaeus, or one of the other two (C. habrosus, C. hastatus)? Worth knowing, though what follows applies to all regardless.] I don't know what "gravel" may refer to here, but anything larger in grain size than very fine river gravel is long-term a problem because anything that adds stress to a fish can exacerbate any other problem. All Corydoradinae species are technically/scientifically termed "filter feeders," and this is an instinct programmed into the fish's DNA and thus important. Smoothness of the substrate is another factor but even if smooth gravel is still problematic; for one thing, bits of food more easily get down where the fish cannot reach it, causing increased bacterial issues for substrate fish. We can move on to the much more critical issues, but keep a change to sand (or another tank with sand for the cories) in mind, and question me later on pursuing this issue if you like.

Water parameters. Temperature at 80F is way too warm for any cories on a permanent basis, and again especially problematic for the dwarf species. [Another brief aside--small sized fish have higher metabolisms, which means they work harder to maintain necessary physiological functioning, and so detriments have more impact too. And as the temperature directly drives the metabolism of each fish, this can be a serious issue.] The temp should be down around 75/76F, absolutely no higher for the cories on a permanent basis (increasing heat to deal with something like ich is temporary). The lower temp will not harm the other named fish, at least no where near as much as the cories.

Another aside (sorry)--don't know how you dealt with the ich, but most soft water species are much more sensitive to many medications, and cories are in this group. Heat, with salt sometimes, is far safer.

The other parameters (GH, KH, pH) are OK for the cories (and cardinals) but are frankly a slow death knell for the two mollies. This fish must have moderately hard or harder water (it cannot be too hard, realistically (GH minimum 12dGH (214 ppm or mg/l) up to 30 dGH (537 ppm or mg/l); the cories and cardinals will not benefit from this though. Straight well water might be best for the mollies depending upon the GH/KH/pH of your well water on its own; I'll move on to the next issue as the GH is not the cory problem, but the additives to achieve it may be.

Re softening the water. Can you explain how you are achieving this? None of the mentioned additives will impact GH/KH, and the comment that the GH is slowly increasing is reason enough to sort out why. Parameters in any fish tank should be quite stable over days, months, even years; this applies to GH, pH and even nitrate [which is not a parameter but a condition and another topic].

I know nothing about aquavitro seed, but the info on their site reads "rapidly and safely establish the aquarium biofilter; synergistic blend of aerobic, anaerobic, and facultative bacteria." This sounds like a nitrifying bacteria supplement of some sort, and if so will not have any impact on GH. And once the aquarium is biologically cycled/balanced, should be unnecessary. Perhaps harmless in its own right, but any substance added to the water without good reason is best not added, as these do impact fish.

The plant additives are a concern. While these can sometimes aid the plants, depending upon the light (light intensity/spectrum alone is what drives photosynthesis, so nutrients just have to be sufficient for the plants' needs in balance with the light), they are still additives to the water and can impact fish, depending. Minimal is always better than excess, which usually means problem algae as well, but no matter; for the sake of all fish, minimal. Substrate tabs for larger rooted plants are a better option for this reason, though floaters and upper water plants obviously gain no benefit for substrate tabs. But it can be surprising how little additives may actually be necessary to keep things balanced. But there is one additive mentioned that is very dangerous, and that is Flourish Excell, and Flourish Iron can be deadly too.

"Flourish" I will assume means the Flourish Comprehensive Supplement for the Planted Aquarium, to give it its full name. I have been using this for years, but carefully. You might well find that Flourish Tabs inserted one next to each of the rooted sword plants, replaced every 3 months, will provide even better response than the liquid alone, it certainly has for me and I have zero GH water so no minerals there. FT do not release nutrients into the upper water column, hence they get to the plants in the substrate but not into the fish.

Iron should absolutely never be added alone, but only in a careful balance with all other required nutrients (there are 13 if memory serves me, all are in FC for a list except oxygen, hydrogen and carbon). Iron is often, or used to be, touted as the plant "cure" but it is only a micro-nutrient, and in FC it is in balance with the others so unnecessary. Iron is a heavy metal, deadly to all fish and plants in excess. And here again, what goes in the water is most likely diffusing across the fish cell membranes and entering the fish's bloodstream. Less is better.

Excell is certainly as bad if not worse. This is glutaraldehyde and water. This substance is used in embalming fluid, antifreeze, ship ballasts to kill bacteria--you get the idea. At bottle-recommended dose levels it usually kills Vallisneria and some other plants which should warn us of its dangers. If overdosed it can kill plants, fish and bacteria. The fact that it is reported to kill brush/beard algae is another warning sign. Nothing like this should ever go in a fish tank.

Which dechlorinator are you using? They are not all equal, believe me. Some contain toxic additives, some need more to work (= more in the water and more inside the fish). May have more when I know.

Hope this helps. And don't discourage, we all learned the above, and we want others to be successful, and not in time give up and leave the hobby as often occurs. I've been there too.

I cannot thank you enough for your detailed response. I have been busy during the week but finally had time to respond today.

On the substrate - I have heard about this many times, but have been told by my pet store that every tank needs corys regardless. Are they really that important to a healthy tank? And if not, would you wager they'd be better off back at the pet store than in my tank?

On temperature - I am in the process of fixing this now, thanks.

On ich - I used ich-x, as it was recommended by my pet store and at the time I didn't have an adjustable heater. Hopefully in the future it will not come up again, but I will be more prepared next time.

On water parameters - I have raised several generations of mollies in this tank, and have only lost 1 due to dropsy, which followed the ich and would seem to be a secondary infection. Not saying I don't believe you, but if it is really this bad for them I'd appreciate an elaboration, and maybe some citations for this.

On water softening - I use a salt-based water softener.

On Seed - I only use this after cleaning my filter and doing a water change, so very sparingly.

On plant additives - I agree with your sentiment, and I have been reticent to use these products, but I just can't get any plants to grow in my tank. The only plant that has done well is duckweed. Everything else has either literally disintegrated into slime, dropped all its leaves and is now just a stem, or grows just enough to keep up with the dying bits and looks quite sickly. I could go more into this, but after reading over what you said it sounds like I need to create a separate thread to address this. Regardless, I appreciate the warning and will pause my usage of these for now, and see how it affects my tank.

On dechlorinator - I use aquavitro alpha.

 

[Gemtrox42]

Could be an issue, particularly with corydoras, if the method of softening water is by using resin that is 'charged' with sodium.
As the resin 'collects' calcium and magnesium, softening the water, they are exchanged for a small amount of sodium. This means that softened water contains a small amount of sodium, also known as salt to which corydoras are notoriously intolerant to.

Yes this is the case, and I appreciate the warning.

 

[Byron]

On the substrate - I have heard about this many times, but have been told by my pet store that every tank needs corys regardless. Are they really that important to a healthy tank? And if not, would you wager they'd be better off back at the pet store than in my tank?

No tank "needs" any type of fish. And the old adage that cories keep a tank clean by eating leftovers is as false as the flat earth concept. Cories need proper cory food. Never acquire a fish unless you want that fish and can provide what the species needs. And don't listen to advice from pet store staff unless you know the knowledge level of the individual--we have all learned this usually the hard way. I cannot tell you to keep or return fish, but the pygmy cories need sand, and proper food (sinking shrimp pellets, Bug Bites are two of the best) to be healthy.

On water softening - I use a salt-based water softener.

Trouble, as someone else noted. Salt is detrimental to all freshwater fish; use in treatment of a specific problem is fine for most fish (always exceptions), but not as a regular additive. What is the GH and pH of the well water straight from the well?

Water Softeners [cited verbatim from Dr. Neale Monks]

“Domestic water softeners do not produce soft water in the sense that aquarists mean. What domestic water softeners do is remove the temporary hardness (such as carbonates) that potentially furs up pipes and heaters by replacing it with permanent hardness (such as chlorides) that does not. While you can pass this softened water through a reverse-osmosis filter to remove the permanent hardness as well, until you have done so, you shouldn't consider the softened water as being suitable for soft water fish.

In fact, aquarists are divided on whether the resulting softened water is safe for keeping fish at all. The odd balance of minerals in softened water is not typical of any of the environments from which tropical fish are collected. While the chloride levels are much higher than those soft water fish are adapted to, the levels of carbonate hardness are too low for the health of hard water fishes like Rift Valley cichlids, goldfish, and livebearers. So the safe approach is not to use it in any aquarium, and instead draw water from the unsoftened drinking water source in the kitchen.”

On plant additives - I agree with your sentiment, and I have been reticent to use these products, but I just can't get any plants to grow in my tank. The only plant that has done well is duckweed. Everything else has either literally disintegrated into slime, dropped all its leaves and is now just a stem, or grows just enough to keep up with the dying bits and looks quite sickly. I could go more into this, but after reading over what you said it sounds like I need to create a separate thread to address this. Regardless, I appreciate the warning and will pause my usage of these for now, and see how it affects my tank.

Yes, a new thread on this topic, but I will just say that the salt is harmful to plants as well as fish. The light may be a factor. And all the additives...I had plants die from using iron, and Excel is known to kill plants.

On dechlorinator - I use aquavitro alpha.

Seachem's website says this conditioner is for saltwater. It also has more risk given how it messes with this and that. I have not come across a better conditioner than API's Tap Water Conditioner. It is the most highly concentrated so less is needed, and it does nothing but deal with chlorine, chloramine and heavy metals. I won't even use Prime because of its messing with ammonia, nitrite and nitrate (in new systems, this is useful but not after) which is the job of the plants and/or the bacteria.

On water parameters - I have raised several generations of mollies in this tank, and have only lost 1 due to dropsy, which followed the ich and would seem to be a secondary infection. Not saying I don't believe you, but if it is really this bad for them I'd appreciate an elaboration, and maybe some citations for this.

Having some of the other info, this may be why your mollies are struggling but surviving more than they otherwise could, given the GH. Here's a link to the SF profile on the black molly, note the water parameter and maintenance data.
Poecilia sphenops – Short-finned Molly/Black Molly — Seriously Fish

To explain how a fish is impacted by the GH is a lesson is fish biology and it will be easier to do a separate post for this.

 

[Byron]

I will cite relevant passages from some of my online articles to hopefully explain the importance of GH on freshwater fish; as these are excerpts, they may overlap, but the basic data should be clear.

Fish live in water, and their bodies contain water; the fish’s cells separate these two waters, but the cells are semi-permeable, which means the cell will permit the movement of water and certain non-polar molecules to pass through either way (called osmosis) but will prevent the passage of larger or charged molecules. The way the water moves is determined by the difference in concentrations between the two waters: water of higher concentration (more dense) will attempt to pass through to the water of lower concentration (less dense) until the two are equal. If the fish could not somehow control this natural flow, it would either rapidly dehydrate or explode. But fish are able to control this through osmoregulation, a complex series of chemical processes. The water moving in or out of the fish’s body will likely have a different pH, so another set of processes controls the function of regulating the pH of the fish’s blood (Muha, 2005). Both of these processes also affect the ability of the blood to carry oxygen, and this impacts many other functions including digestion, the immune system, and so on.

The kidneys primarily work to eliminate excess water, but another function is the conservation and reabsorption of essential salts. Both processes work to maintain a specific salt/water balance. This osmoregulation of bodily fluids requires a great amount of metabolic energy. So a high osmotic pressure (caused by elevated levels of TDS outside the fish’s natural range) will overwhelm the fish with excess water and overwork the kidneys, while a low osmotic pressure (caused by TDS levels below those of the fish’s natural range) will deprive the fish of the water needed for the kidney functions (Evans, 2004).

Water hardness is the measure of dissolved mineral salts in the water, a portion of the TDS (total dissolved solids). There are two basic types of hardness of importance to aquarists, termed general hardness (abbreviated GH) and carbonate hardness (abbreviated KH, from the German “karbon” [carbon]). The combined GH and KH is sometimes termed “total hardness,” but this is of less importance because the GH and KH individually impact the water in different ways. General Hardness is determined primarily by the minerals calcium and magnesium; GH is sometimes referred to as “permanent hardness” because it cannot be removed from water by boiling as can KH. Fish are directly impacted by GH and TDS; their growth, the transfer of nutrients and waste products through cell membranes, spawning (sperm transfer, egg fertility or hatching), and the proper functioning of internal organs such as the kidneys can all be affected.

Hard water species must have calcium and magnesium present in the water in order for their kidneys to function, and beyond that. They have no means of getting this except from the water entering their bodies. As this water passes through the kidneys, the process of osmoregulation determines how the water is processed. Mineral salts like the calcium are extracted by the kidneys. In hard water species these mineral salts are essential to the proper functioning of the internal processes that work continually to maintain the fish's equilibrium; without these minerals the fish slowly weakens and dies. In fishes evolved in soft water, the salts are "foreign substances" that the fish does not have the ability to deal with, simply because it was never designed to do so. Calcium builds up, blocking the kidneys, and the fish dies.

The fish's internal biological processes are governed by the environmental factors mentioned above. The fish must for example regulate the pH of its blood to equal that of the water in which it lives, ensure the tissues are fed, the immune system functions, etc. The fish's physiology depends upon factors determined by the environment. As soon as these factors are changed from what the fish is programmed and designed to use, it creates stress, but even more significantly, the fish must expend considerable energy attempting to "right" what is "wrong." And generally it cannot do this, at least not for long, or depending upon the degree of difference. This means the fish slowly weakens. Usually the severe failure of the immune system causes the fish to die from some disease or issue that it normally should have easily dealt with, but could not because of its weakened state. In all cases, should the fish somehow miraculously succeed in avoiding disease, it has been weakened to such a degree that it can no longer support life processes and it dies, prematurely. There are no external signs of any of this, until the fish dies. Necropsy (autopsy in animals) can determine exactly which process failed.

The author (Laura Muha, 2005) of an article in TFH a few years back had a good analogy. The fish living in the environment for which it is designed by evolution is comparable to a car traveling along at say 30km per hour on a level road. Everything is working well, and the car reaches its end goal. But if it encounters a "foreign obstacle" like a steep hill, it must immediately kick into overdrive, and use considerably more energy to maintain the same level of speed. Thus the fish encountering any environmental factor that is outside its preference has to kick into high gear in an attempt to maintain the essential bodily functions of life. Most fish, depending upon the degree and other factors like size (larger fish species have better ability than smaller fish species), can maintain this heightened state for a brief period, to get them through some immediate problem, but not for long. The fish weakens the longer it is forced into this situation, until it simply can no longer cope.

 

[AdoraBelle Dearheart]

I will cite relevant passages from some of my online articles to hopefully explain the importance of GH on freshwater fish; as these are excerpts, they may overlap, but the basic data should be clear.

Fish live in water, and their bodies contain water; the fish’s cells separate these two waters, but the cells are semi-permeable, which means the cell will permit the movement of water and certain non-polar molecules to pass through either way (called osmosis) but will prevent the passage of larger or charged molecules. The way the water moves is determined by the difference in concentrations between the two waters: water of higher concentration (more dense) will attempt to pass through to the water of lower concentration (less dense) until the two are equal. If the fish could not somehow control this natural flow, it would either rapidly dehydrate or explode. But fish are able to control this through osmoregulation, a complex series of chemical processes. The water moving in or out of the fish’s body will likely have a different pH, so another set of processes controls the function of regulating the pH of the fish’s blood (Muha, 2005). Both of these processes also affect the ability of the blood to carry oxygen, and this impacts many other functions including digestion, the immune system, and so on.

The kidneys primarily work to eliminate excess water, but another function is the conservation and reabsorption of essential salts. Both processes work to maintain a specific salt/water balance. This osmoregulation of bodily fluids requires a great amount of metabolic energy. So a high osmotic pressure (caused by elevated levels of TDS outside the fish’s natural range) will overwhelm the fish with excess water and overwork the kidneys, while a low osmotic pressure (caused by TDS levels below those of the fish’s natural range) will deprive the fish of the water needed for the kidney functions (Evans, 2004).

Water hardness is the measure of dissolved mineral salts in the water, a portion of the TDS (total dissolved solids). There are two basic types of hardness of importance to aquarists, termed general hardness (abbreviated GH) and carbonate hardness (abbreviated KH, from the German “karbon” [carbon]). The combined GH and KH is sometimes termed “total hardness,” but this is of less importance because the GH and KH individually impact the water in different ways. General Hardness is determined primarily by the minerals calcium and magnesium; GH is sometimes referred to as “permanent hardness” because it cannot be removed from water by boiling as can KH. Fish are directly impacted by GH and TDS; their growth, the transfer of nutrients and waste products through cell membranes, spawning (sperm transfer, egg fertility or hatching), and the proper functioning of internal organs such as the kidneys can all be affected.

Hard water species must have calcium and magnesium present in the water in order for their kidneys to function, and beyond that. They have no means of getting this except from the water entering their bodies. As this water passes through the kidneys, the process of osmoregulation determines how the water is processed. Mineral salts like the calcium are extracted by the kidneys. In hard water species these mineral salts are essential to the proper functioning of the internal processes that work continually to maintain the fish's equilibrium; without these minerals the fish slowly weakens and dies. In fishes evolved in soft water, the salts are "foreign substances" that the fish does not have the ability to deal with, simply because it was never designed to do so. Calcium builds up, blocking the kidneys, and the fish dies.

The fish's internal biological processes are governed by the environmental factors mentioned above. The fish must for example regulate the pH of its blood to equal that of the water in which it lives, ensure the tissues are fed, the immune system functions, etc. The fish's physiology depends upon factors determined by the environment. As soon as these factors are changed from what the fish is programmed and designed to use, it creates stress, but even more significantly, the fish must expend considerable energy attempting to "right" what is "wrong." And generally it cannot do this, at least not for long, or depending upon the degree of difference. This means the fish slowly weakens. Usually the severe failure of the immune system causes the fish to die from some disease or issue that it normally should have easily dealt with, but could not because of its weakened state. In all cases, should the fish somehow miraculously succeed in avoiding disease, it has been weakened to such a degree that it can no longer support life processes and it dies, prematurely. There are no external signs of any of this, until the fish dies. Necropsy (autopsy in animals) can determine exactly which process failed.

The author (Laura Muha, 2005) of an article in TFH a few years back had a good analogy. The fish living in the environment for which it is designed by evolution is comparable to a car traveling along at say 30km per hour on a level road. Everything is working well, and the car reaches its end goal. But if it encounters a "foreign obstacle" like a steep hill, it must immediately kick into overdrive, and use considerably more energy to maintain the same level of speed. Thus the fish encountering any environmental factor that is outside its preference has to kick into high gear in an attempt to maintain the essential bodily functions of life. Most fish, depending upon the degree and other factors like size (larger fish species have better ability than smaller fish species), can maintain this heightened state for a brief period, to get them through some immediate problem, but not for long. The fish weakens the longer it is forced into this situation, until it simply can no longer cope.

@Essjay @Chad or another mod, would it be possible to have this portion from Byron's excellent post about the effects of water hardness on fish physiology pinned somewhere for easy linking by any chance, please? Would be great to have a pinned thread where people could link any other scientific literature they find that backs up our claims about GH being important... It can be hard to explain to people new in the hobby or those who say that their fish are "fine" in the water hardness they have that the fish might appear fine, but be suffering internal issues.

 

[Chad]

Thanks for asking. I and the mod team will take a look at them and decide.

Chad

 

[Byron]

Thanks for asking. I and the mod team will take a look at them and decide.

Chad

That post was a hodge-podge of bits from some of my articles, not really coherent. Might be best to leave it.

 

[Chad]

That post was a hodge-podge of bits from some of my articles, not really coherent. Might be best to leave it.

Thanks for chiming in. If you have a version you feel comfortable being pinned, let us know.

 

[Gemtrox42]

Trouble, as someone else noted. What is the GH and pH of the well water straight from the well?

GH is between 150 and 300ppm, hard to tell with test strips, as the range between colors is quite large towards the higher end. PH is about 7.4. Is there a more precise GH measurement you could recommend?
Also - it seems like the GH and PH requirements for Molly's and cardinals are different. Should they even be in the same tank?

So, back on topic, to summarize the gravel bottom, temperature, salinity, and plant/water additives are the probable culprits for cory behavior differences. I will open a new thread on plants, the temp I have fixed, my wellwater I will use unconditioned from now on. Only problem is gravel bottom. May have to get a new tank with sand for them then.

 

[Byron]

GH is between 150 and 300ppm, hard to tell with test strips, as the range between colors is quite large towards the higher end. PH is about 7.4. Is there a more precise GH measurement you could recommend?

If the actual GH is close to the lower number (150), this would be moderately soft and the cardinals and other soft water fish should be OK. But the mollies will continue to struggle, and worsen. If the actual GH is closer to the high number (300), the mollies would be thriving but the cardinals would not. The pH is so "average" it should not be much to worry about, it is the GH that matters.

Also - it seems like the GH and PH requirements for Molly's and cardinals are different. Should they even be in the same tank?

No, they should not. This is why so many of us here first ask about GH (and pH while at it) when members ask about this or that fish. When you have fish requiring two very different environments in order to be healthy and less stressed, there is often no "middle ground." There are exceptions, as there are always exceptions in life, but when it comes to the freshwater fish physiology they have their limits.

So, back on topic, to summarize the gravel bottom, temperature, salinity, and plant/water additives are the probable culprits for cory behavior differences.

Yes. And I think I can forecast problems for the other soft water species with respect to the salinity, plant/water additives. Characins have an equal sensitivity to chemicals in the water. Their physiology is again the reason, but explaining that would be another essay! No problem if interested.

If you do decide on another tank, consider combining the soft water species together since they have identical water requirements (and sand is ideal as a substrate for any of our fish and plants). One option, as the cories will like company; my group of pygmy cories swim in the upper water column all the time with my Ember Tetras and Green neons.

 

[Gemtrox42]

OK, I found a 10 gal I can use. I'm assuming if you keep tetras and neons with your corys the cardinals should move with them. In that case, is 10 gal too small for 14 tetras and 5 corys?