plebian
Fish Fanatic
I'm posting this here, because although the focus is on discus, it contains useful information for all fish keepers.
Following are some basic facts about discus that any prospective, or current, discus keeper should know. I want to emphasize the items listed below are facts, not opinions:
1) Contrary to most reports, discus are not just blackwater fish. Discus inhabit all Amazonian river types including blackwater, clearwater, and whitewater. The waters in these rivers vary in pH from 4.0 – 7.0 while dissolved mineral content (water hardness) varies from less than 10 ppm to more than 100 ppm.
2) In the ecosystems most commonly inhabited by discus, the only living plants they encounter (aside from algae) are terrestrial plants that have been covered by seasonal flood waters. During low water seasons, discus typically gather around submerged dead trees for protection against predators.
3) Discus are classified as omnivores, but in those few areas that have been studied, their primary source of food is detritus (algae and decaying plant matter). Typically, only a small fraction of their diet consists of animal protein, primarily insect larvae and other micro-invertebrates.
4) Adult discus can tolerate very hard water (greater than 300 ppm) without any ill effects. I’ve read several reports from reliable sources who claim they have kept discus in “liquid rock” for many years without any problems. Following is a quote from a well respected European breeder:
“...from the experience of my customers, who have different water values all over the world and from conversations with professionals from aquaculture, the conductance does not seem to play a major role as long as it is fresh water. Even fish from soft water areas seem to be very adaptable. I heard the most extreme values from Israel, where an acquaintance raised hundreds of thousands of discus fish with conductance values between 800 and 1200 micro siemens and they were very healthy. So before you try to lower your tap water from 550 micro siemens to 200, just leave it at that. It is cheaper, easier and does not run the risk of getting bacteria into the aquarium from contaminated osmosis systems, demineralizers or from activated carbon filters and cartridge filters. This is much more dangerous for the fish than a few hundred micro siemens more.”
5) Farm raised discus are typically grown out in water with a pH from 7.0 – 7.5 and water hardness between 100 – 200 ppm. I am not aware of any discus farm that uses RO water except for breeding purposes. It’s simply too expensive to do so (not to mention wasteful). I have had discus lay eggs in water as hard as 350 ppm, with a pH as high as 7.7, though they did not produce fry. Discus eggs will not develop in hard water. This is true of many Amazonian fishes, though I have bred diamond tetras in water like this. Egg development is generally the issue, not the health of adult fish. Breeding is the only reason to use RO water.
6) Discus exhibit a wide range of personalities, from extremely aggressive to extremely timid.
It is important for beginning discus keepers to keep this last point in mind. Some discus can also be very fussy about food. Others will eat just about anything you give them. My current crop of discus are very fond of algae. They also consume detritus, including sometimes their own feces. Presumably that’s because it contained some undigested bits. It took almost two weeks before they paid any attention to dry food.
A previous group of discus, from the same breeder, would not touch algae, with the exception of one individual. This individual also ignored dry food, but all the others consumed it voraciously. Even after introducing some blood worms to their diet, most of the discus continued to willingly consume dry food. This is not always the case. Some discus become addicted to blood worms and will not eat anything else to the point of starvation.
All healthy discus will exhibit some level of aggression. This typically does not become apparent until juveniles approach 4 months of age. The competition for dominance within the group at this age can be unsettling for the inexperienced. In most cases, the discus sort things out after a month or two without any negative consequences. Sometimes it takes a bit longer.
This, however, is not always the case. One group of discus I kept included a dominant male and a smaller female he was mating with. Most of the sparring had played itself out prior to the pairing, but another, larger female, disputed this arrangement. She repeatedly attacked the smaller female in an attempt to drive her away. This was in spite of efforts by the male partner to intervene, sometimes shielding his partner from attacks with his body or engaging in mouth to mouth combat with the offending female.
Initially, I planned on letting things play out. Unfortunately, the aggressive female continued her attacks every hour, of every day, over a period of one month. It was not only disrupting the lives of the mating pair, it was disrupting the normal social interactions of the other discus. I finally had to remove the aggressor. Once this was done, group behavior normalized and all was well.
With another group, there was one aggressive fish and three other very timid fish. The timid fish were so intimidated they refused to eat. This was the case even though the aquarium they were being kept in was very spacious and food was being distributed throughout with plenty of opportunity to grab something to eat while the aggressor was occupied elsewhere. Instead, the timid ones would collect together under some driftwood and refuse to come out regardless of where the aggressor was foraging.
After several weeks, these juveniles were showing early signs of emaciation. They would almost certainly grow up stunted unless something changed. I could remove the aggressive fish, the largest and most beautiful of the group, and hope the others would eventually recover, or I could replace the timid fish with a new group of juveniles and hope they would be more tolerant of the aggression. In either case, a positive outcome was unlikely, so I replaced the entire group.
I have spoken at some length about discus behavior without ever mentioning diseases. I did this because in my opinion behavioral issues are more common that disease among discus, assuming they are kept in a healthy environment. I have never seen any of the diseases or parasites commonly mentioned on websites and forums among any of the fish I’ve kept, including discus, with two exceptions:
1) Whirling disease, which I believe is genetic in origin, much like epilepsy in humans, and seems to plague discus in particular.
2) Gill flukes, which seem to be a common problem. All of the discus I’ve purchased in recent years. Those discus came from 3 different farms located in 3 different countries. I’m not sure why gill flukes are such a problem, though I do know they are extremely difficult to eradicate.
In any case, some fish will become seriously infested to the point of displaying swollen gills and heavy breathing, while others will display few if any outward symptoms. I assume this is attributable to inherited immunity. The one study of gill flukes among wild discus that I am aware of reported a 14% rate of parasitic infection. Another much smaller study of farmed discus reported an infection rate of 35%.
I mentioned the importance of a healthy environment. As seems to be the case with any and all topics concerning fish keeping, there are a lot of opinions about this and a lot of misinformation.
First off, any pH 5.0 – 8.0 is perfectly fine for the vast majority of species available to hobbyists. Even rapid changes in pH, so long as they are not extreme, are well tolerated. For example, I received a group of wild caught tetras that arrived in water with pH measuring 7.0 and performed a “plop and drop” into water with a pH of 7.7.
Not only were the fish unaffected by the rapid change in pH, but their color improved dramatically within minutes, simply by being removed from the more stressful environment of a plastic bag that had just spent four hours being jostled on the road.
The same can be said about temperature and water hardness. I’ve already discussed the issue of water hardness, so I’ll address temperature. I was transporting some discus I had just purchased and was worried about heat build up in the back of my all black hatchback. The weather was hot, and I expected it to get hotter as I traveled south. I decided to add some ice to the foam boxes the fish were being transported in.
Ironically, the weather actually cooled the farther south I drove. I started to worry I may have added too much ice, but since the time to destination was less than fours, I continued onward.
When I got home and opened the box, I could tell immediately the water was much too cold. I was too concerned to actually measure the temperature, but my best guess is that it was no more than 22C, possibly colder. I immediately removed the discus and transferred them to their new home, where the water was 29C. The discus began coloring up almost immediately.
The truth is, I have never “acclimated” any of the fish I have acquired over the years. In addition to discus, this includes several species of dwarf African cichlids, several species of dwarf catfish including Corydoras, several species of tetras, guppies and goldfish. Nor have I ever experienced any disease issues other then the two exceptions noted above.
In the beginning, it was simply out of ignorance, but after years of experience without any ill effects I was skeptical of all the recommendations to acclimate I’ve come across since the advent of Internet forums. What little research there is on the topic confirms my own experience.
I actually came across a video of a large reseller showing how they handle incoming discus. It was all “plop and drop”. Previously they went through the process of acclimation, but after years of experience found it was not only a pointless wasted of time, but counterproductive. The water the fish had been transported in was much more stressful than the transfer to clean water, regardless of parameters.
What follows is more opinion than fact, though it is based on my personal experience, the experience of two respected discus farms, and a great deal of relevant research and reasonable supposition.
What’s most important about water parameters is stability over time, not the actual numbers. The only generalization about discus that holds true is that they must be kept in warmer water, over the long term, than most other tropical fish species. They really do need to be kept within the temperature range of 28-30C over the long term for optimal well being. Occasional dips above or below those parameters are a non issue, but you will notice an observable difference in behavior if the temperatures vary too much outside that range over an extended period.
Other than that, the single most effective thing a hobbyist can do for discus is to maintain healthy water. This is true for all fish, not just discus. This does not mean daily water changes. It does not mean keeping nitrates below 10 ppm as many claim. In truth, even juvenile discus will do well in water with nitrate as high as 80 ppm. The same breeder mentioned above keeps his discus in water with nitrate measuring between 25 – 150 ppm.
Discus, or any other species, are not nearly as sensitive to nitrate as most Internet sources are reporting. One of the largest and oldest discus farms in Europe used to boast that they kept adult discus in water with nitrate as high as 200 ppm, while they raised discus fry in water with nitrate between 25-50 ppm.
What discus are sensitive to is bacterial loading, the number of heterotrophic bacteria living in the water column. This is true for all fish, it’s just that discus seem to be a bit more sensitive to this than other species. I suspect this has a lot to do with them having evolved in waters with a low bacteria count, not to mention the nearly sterile conditions breeders raise their fry in mentioned above. Their immune systems just haven’t evolved to handle it.
Providing water with a low bacterial load is as simple as it is magical. I simply don’t have the time, nor am I willing to spend the effort to get into the magical part. In all likelihood, this post will get buried beneath an immense amount of nonsense that accumulates on this site almost daily, not to mention the relentless argument so common on Internet forums, so there is no point.
In short, whatever filtration you are using, it must be capable of removing not just ammonia and nitrite, but most of the dissolved organic matter (DOM) in the water column that provides food for heterotrophic bacteria.
To do this one requires stable water parameters and enough filter media surface area to support not just nitrifying bacteria, but sufficient heterotrophic bacteria (among many other species of microbes) to remove the DOM from the water column (including potential pathogens). It requires very little biological activity to remove ammonia and nitrite. It requires a great deal more to remove DOM.
My own preference for filtration is UGF, because of its simplicity, reliability, and low cost. My current UGF, covered with 2” of 3-5 mm quartz gravel, has proved more efficient than two very large canister filters filled with the most efficient filter media available (30 PPI foam). The key is using the smallest gravel size possible. The larger the gravel, the less there is of usable surface area.
Sumps are a great alternative. I won’t say any more on the matter. All I can say is do your research.
Following are some basic facts about discus that any prospective, or current, discus keeper should know. I want to emphasize the items listed below are facts, not opinions:
1) Contrary to most reports, discus are not just blackwater fish. Discus inhabit all Amazonian river types including blackwater, clearwater, and whitewater. The waters in these rivers vary in pH from 4.0 – 7.0 while dissolved mineral content (water hardness) varies from less than 10 ppm to more than 100 ppm.
2) In the ecosystems most commonly inhabited by discus, the only living plants they encounter (aside from algae) are terrestrial plants that have been covered by seasonal flood waters. During low water seasons, discus typically gather around submerged dead trees for protection against predators.
3) Discus are classified as omnivores, but in those few areas that have been studied, their primary source of food is detritus (algae and decaying plant matter). Typically, only a small fraction of their diet consists of animal protein, primarily insect larvae and other micro-invertebrates.
4) Adult discus can tolerate very hard water (greater than 300 ppm) without any ill effects. I’ve read several reports from reliable sources who claim they have kept discus in “liquid rock” for many years without any problems. Following is a quote from a well respected European breeder:
“...from the experience of my customers, who have different water values all over the world and from conversations with professionals from aquaculture, the conductance does not seem to play a major role as long as it is fresh water. Even fish from soft water areas seem to be very adaptable. I heard the most extreme values from Israel, where an acquaintance raised hundreds of thousands of discus fish with conductance values between 800 and 1200 micro siemens and they were very healthy. So before you try to lower your tap water from 550 micro siemens to 200, just leave it at that. It is cheaper, easier and does not run the risk of getting bacteria into the aquarium from contaminated osmosis systems, demineralizers or from activated carbon filters and cartridge filters. This is much more dangerous for the fish than a few hundred micro siemens more.”
5) Farm raised discus are typically grown out in water with a pH from 7.0 – 7.5 and water hardness between 100 – 200 ppm. I am not aware of any discus farm that uses RO water except for breeding purposes. It’s simply too expensive to do so (not to mention wasteful). I have had discus lay eggs in water as hard as 350 ppm, with a pH as high as 7.7, though they did not produce fry. Discus eggs will not develop in hard water. This is true of many Amazonian fishes, though I have bred diamond tetras in water like this. Egg development is generally the issue, not the health of adult fish. Breeding is the only reason to use RO water.
6) Discus exhibit a wide range of personalities, from extremely aggressive to extremely timid.
It is important for beginning discus keepers to keep this last point in mind. Some discus can also be very fussy about food. Others will eat just about anything you give them. My current crop of discus are very fond of algae. They also consume detritus, including sometimes their own feces. Presumably that’s because it contained some undigested bits. It took almost two weeks before they paid any attention to dry food.
A previous group of discus, from the same breeder, would not touch algae, with the exception of one individual. This individual also ignored dry food, but all the others consumed it voraciously. Even after introducing some blood worms to their diet, most of the discus continued to willingly consume dry food. This is not always the case. Some discus become addicted to blood worms and will not eat anything else to the point of starvation.
All healthy discus will exhibit some level of aggression. This typically does not become apparent until juveniles approach 4 months of age. The competition for dominance within the group at this age can be unsettling for the inexperienced. In most cases, the discus sort things out after a month or two without any negative consequences. Sometimes it takes a bit longer.
This, however, is not always the case. One group of discus I kept included a dominant male and a smaller female he was mating with. Most of the sparring had played itself out prior to the pairing, but another, larger female, disputed this arrangement. She repeatedly attacked the smaller female in an attempt to drive her away. This was in spite of efforts by the male partner to intervene, sometimes shielding his partner from attacks with his body or engaging in mouth to mouth combat with the offending female.
Initially, I planned on letting things play out. Unfortunately, the aggressive female continued her attacks every hour, of every day, over a period of one month. It was not only disrupting the lives of the mating pair, it was disrupting the normal social interactions of the other discus. I finally had to remove the aggressor. Once this was done, group behavior normalized and all was well.
With another group, there was one aggressive fish and three other very timid fish. The timid fish were so intimidated they refused to eat. This was the case even though the aquarium they were being kept in was very spacious and food was being distributed throughout with plenty of opportunity to grab something to eat while the aggressor was occupied elsewhere. Instead, the timid ones would collect together under some driftwood and refuse to come out regardless of where the aggressor was foraging.
After several weeks, these juveniles were showing early signs of emaciation. They would almost certainly grow up stunted unless something changed. I could remove the aggressive fish, the largest and most beautiful of the group, and hope the others would eventually recover, or I could replace the timid fish with a new group of juveniles and hope they would be more tolerant of the aggression. In either case, a positive outcome was unlikely, so I replaced the entire group.
I have spoken at some length about discus behavior without ever mentioning diseases. I did this because in my opinion behavioral issues are more common that disease among discus, assuming they are kept in a healthy environment. I have never seen any of the diseases or parasites commonly mentioned on websites and forums among any of the fish I’ve kept, including discus, with two exceptions:
1) Whirling disease, which I believe is genetic in origin, much like epilepsy in humans, and seems to plague discus in particular.
2) Gill flukes, which seem to be a common problem. All of the discus I’ve purchased in recent years. Those discus came from 3 different farms located in 3 different countries. I’m not sure why gill flukes are such a problem, though I do know they are extremely difficult to eradicate.
In any case, some fish will become seriously infested to the point of displaying swollen gills and heavy breathing, while others will display few if any outward symptoms. I assume this is attributable to inherited immunity. The one study of gill flukes among wild discus that I am aware of reported a 14% rate of parasitic infection. Another much smaller study of farmed discus reported an infection rate of 35%.
I mentioned the importance of a healthy environment. As seems to be the case with any and all topics concerning fish keeping, there are a lot of opinions about this and a lot of misinformation.
First off, any pH 5.0 – 8.0 is perfectly fine for the vast majority of species available to hobbyists. Even rapid changes in pH, so long as they are not extreme, are well tolerated. For example, I received a group of wild caught tetras that arrived in water with pH measuring 7.0 and performed a “plop and drop” into water with a pH of 7.7.
Not only were the fish unaffected by the rapid change in pH, but their color improved dramatically within minutes, simply by being removed from the more stressful environment of a plastic bag that had just spent four hours being jostled on the road.
The same can be said about temperature and water hardness. I’ve already discussed the issue of water hardness, so I’ll address temperature. I was transporting some discus I had just purchased and was worried about heat build up in the back of my all black hatchback. The weather was hot, and I expected it to get hotter as I traveled south. I decided to add some ice to the foam boxes the fish were being transported in.
Ironically, the weather actually cooled the farther south I drove. I started to worry I may have added too much ice, but since the time to destination was less than fours, I continued onward.
When I got home and opened the box, I could tell immediately the water was much too cold. I was too concerned to actually measure the temperature, but my best guess is that it was no more than 22C, possibly colder. I immediately removed the discus and transferred them to their new home, where the water was 29C. The discus began coloring up almost immediately.
The truth is, I have never “acclimated” any of the fish I have acquired over the years. In addition to discus, this includes several species of dwarf African cichlids, several species of dwarf catfish including Corydoras, several species of tetras, guppies and goldfish. Nor have I ever experienced any disease issues other then the two exceptions noted above.
In the beginning, it was simply out of ignorance, but after years of experience without any ill effects I was skeptical of all the recommendations to acclimate I’ve come across since the advent of Internet forums. What little research there is on the topic confirms my own experience.
I actually came across a video of a large reseller showing how they handle incoming discus. It was all “plop and drop”. Previously they went through the process of acclimation, but after years of experience found it was not only a pointless wasted of time, but counterproductive. The water the fish had been transported in was much more stressful than the transfer to clean water, regardless of parameters.
What follows is more opinion than fact, though it is based on my personal experience, the experience of two respected discus farms, and a great deal of relevant research and reasonable supposition.
What’s most important about water parameters is stability over time, not the actual numbers. The only generalization about discus that holds true is that they must be kept in warmer water, over the long term, than most other tropical fish species. They really do need to be kept within the temperature range of 28-30C over the long term for optimal well being. Occasional dips above or below those parameters are a non issue, but you will notice an observable difference in behavior if the temperatures vary too much outside that range over an extended period.
Other than that, the single most effective thing a hobbyist can do for discus is to maintain healthy water. This is true for all fish, not just discus. This does not mean daily water changes. It does not mean keeping nitrates below 10 ppm as many claim. In truth, even juvenile discus will do well in water with nitrate as high as 80 ppm. The same breeder mentioned above keeps his discus in water with nitrate measuring between 25 – 150 ppm.
Discus, or any other species, are not nearly as sensitive to nitrate as most Internet sources are reporting. One of the largest and oldest discus farms in Europe used to boast that they kept adult discus in water with nitrate as high as 200 ppm, while they raised discus fry in water with nitrate between 25-50 ppm.
What discus are sensitive to is bacterial loading, the number of heterotrophic bacteria living in the water column. This is true for all fish, it’s just that discus seem to be a bit more sensitive to this than other species. I suspect this has a lot to do with them having evolved in waters with a low bacteria count, not to mention the nearly sterile conditions breeders raise their fry in mentioned above. Their immune systems just haven’t evolved to handle it.
Providing water with a low bacterial load is as simple as it is magical. I simply don’t have the time, nor am I willing to spend the effort to get into the magical part. In all likelihood, this post will get buried beneath an immense amount of nonsense that accumulates on this site almost daily, not to mention the relentless argument so common on Internet forums, so there is no point.
In short, whatever filtration you are using, it must be capable of removing not just ammonia and nitrite, but most of the dissolved organic matter (DOM) in the water column that provides food for heterotrophic bacteria.
To do this one requires stable water parameters and enough filter media surface area to support not just nitrifying bacteria, but sufficient heterotrophic bacteria (among many other species of microbes) to remove the DOM from the water column (including potential pathogens). It requires very little biological activity to remove ammonia and nitrite. It requires a great deal more to remove DOM.
My own preference for filtration is UGF, because of its simplicity, reliability, and low cost. My current UGF, covered with 2” of 3-5 mm quartz gravel, has proved more efficient than two very large canister filters filled with the most efficient filter media available (30 PPI foam). The key is using the smallest gravel size possible. The larger the gravel, the less there is of usable surface area.
Sumps are a great alternative. I won’t say any more on the matter. All I can say is do your research.
