Help... My Cory Cats Are Dying

[robertsmith50]

Hello all. I am new to the board. I have been keeping fish my entire life (53 years), So I have quite a bit of experience. However, I am having a problem with my new tank that has been set up for about 7 weeks that I have never experienced before. It is a community tank with a little bit of everything. Most of my corydoris catfish have died at the rate of about 2 to 3 a day for the last 5 days. I have also lost one zebra danio and one glo-fish danio, but mostly the corys, or bottom dwellers. The only bottom dwellers that seem to be immune to the problem are my clown loaches.
  Ok...It is a 125 gal tank that has been set up for about 7 weeks. It has a canister filter with 5 trays filled with bio donut things and 2 mechanical sponge filter pads, and I run a PVC pipe type undergravel filter that covers the entire tank floor. I don't run any carbon in the filter. The ammonia levels are 0, nitrate and nitrite at or very near zero at all times. The water here is very hard, but that has not caused any problems in the past. The Ph is 7.0 . I usually do a water change of about 3/4 of the tank every 4 weeks or so. After a water change, the filter gets the water crystal clear over the next 12 hours... much clearer than the tap water it starts with. So the water seems to be as healthy as I can get it, yet for some reason the bottom dwelling fish are dying.
  Everything I have been doing in the past has served me very well, so I tend not to change things unless I have a good reason. There are 2 things that are different than usual right now that are worth mentioning.
First, there are what look like little pieces of white fuzz floating in the water (see pics attached at the bottom of this post) that the canister filter are not sucking up (even though it is a fairly strong filter pump), and I can only assume that some of it is getting pulled into the gravel by the undergravel filter. When they are floating in the water they look white and fluffy, yet when I took some out for the pictures they are actually kind of a dark gray. If you back away from the aquarium a few feet, they look just like frozen brine shrimp floating in the water.
   And the second thing that is different is that I haven't run air (Wands and stones) until I set up this tank. I now have quite a bit of air to help churn up the surface of the water rather than churning with water pumps as before. I was assuming that it would be healthier for the fish to use air. The fish always have plenty of oxygen and all the other fish seem fine and don't appear to be under any stress. I do use stress coat after each water change or when adding new fish and water conditioner to make the tap water safe. When I set up this tank I also used (for the first time) some nitrifying bacteria to help jump start the bio system, which seemed to work fairly well.
   I also added some "general cure" fish meds just in case I was dealing with a parasite, but I have not had good luck with it in the past. So anyways, if anybody has any suggestions or ideas, or needs more info, just let me know. I am completely stumped by this one. I love Cory cats, but I can't in good faith add any more until I get a handle on what's going on. Now, hopefully these pics will post properly. Thanks. Oh, and the plants are all artificial as well. Also, there are powerheads powering the undergravel filter.
 
Bob
 



 

 

[robertsmith50]

Also, temp was 82 degrees when this all started. I tried lowering to 77, but still lost another 4 fish after that. What is a healthy temp for a community tanks?

 

[Byron]

Hi Bob,
 
I have a couple suggestions, but first a couple questions.  How long have you had the corys, including the ones that have died?  Have you had corys in the past that were OK (corys should live for close to 10 years and more)?  What species do you now have?  Which water conditioner are you using?  Do you know the GH of your tap water (you can get this from the water authority, probably on their website)?
 
While waiting for these answers, I will mention a couple things I see as problems.  Now, I am not suggesting that any one of these is going to kill off corys or other fish, but they are individual issues that will add stress to the fish and cumulatively this can cause death.
 
First thing is the temperature...most corys will not last at such warm temperatures.  Without knowing the species, I would get the tank temperature down to 76/77/78 maximum (which I gather from your second post you have).  If there are other fish that need more warmth, you will need to separate these as a temperature around 80F is going to weaken many fish including most corys.  Corydoras sterbai and a few others can manage with 80-82F, but most of the species cannot.  Higher temperatures increase fish metabolism, significantly, because the fish are ectothermal, and this means the fish are going to be working much harder just to maintain their physiological balance.  This takes a toll fairly quickly.
 
Second issue is the StressCoat.  This is not a good substance to be adding to an aquarium with fish, regardless of what API may say.  It contains aloe vera, and this substance affects the fish's gills, literally gumming them up, and can lead to death.  I mentioned this in another thread only last week, and as I cannot now find that thread, I will cut/paste the relevant bit of a 2011 study which sets out the danger:
 
Some additives contain aloe extract from leaves of the Aloe vera plant. Manufacturers of these products claim that the Aloe vera extract promotes healing of damaged tissue. One potential drawback to water additives that contain Aloe vera extract or CMC is the addition of organic waste load that can reduce the water quality and oxygen levels in a closed system. This may not be an issue, depending on the density of fish, length of time fish are held, and oxygen content of the water. However, the effects of these substances on gill tissue are unclear. Taiwo et al. (2005) tested the survival and behavior of tilapia (Oreochromis niloticus) exposed to different concentrations of aqueous extract of A. vera for up to 96 h. One hundred percent of tilapia exposed to 50 ppm A. vera died within the duration of the experiment. Fish used in this experiment exhibited severe depigmentation and destruction of organs (including gills). The evidence of the toxic effects of A. vera on fish solidifies the need to empirically test water conditioners, and their chemical components, for potential negative effects on fish.
 
Third, I would increase the frequency of water changes, to no less than once a week.  I change roughly 50-60% of all my tanks once each week, and I know there are immense benefits.  Here again, it is a matter of keeping the fish healthier over the long term, which lessens stress and thus makes them more resilient to actual disease issues.  I'v been doing this for 20+ years now.
 
I've no idea what the specks are, but would not think this the issue, though that is just surmise.
 
 
Edit.  Just remembered something else...you mention nitrate and nitrite "at or very near zero,"...if nitrite (with the i) is at any level above zero, there is trouble for fish.  As 7 weeks was mentioned, I am wondering if the nitrification cycle is still establishing.  Corys are highly sensitive fish, to everything and anything in the water.
 
Byron.

 

[eaglesaquarium]

A few things jump out at me:
 

• 3/4 of the tank every 4 weeks is just not enough of a water change.
• the temp is far too high for nearly ALL corydoras species.  Most prefer the mid-70s, but some will be the low-70s while a very few others in the higher 70s.  Only sterbai cories can handle the higher temps, as I recall - though there is probably one or two others.
• the undergravel filter.
• The substrate is not appropriate for cories.

 
Water changes should be between 25-50% weekly.  
 
 
The undergravel filter could be the problem (or acerbating it, based on the temp issue).  If you aren't actively removing the detritus that gets into the undergravel filter as well as you possibly can... this could be leading to bacterial infections for the cories.  
 
Cories are bottom dwellers that seek food in the substrate by stuffing their faces into it.  An undergravel filter is likely the worst option for them, as they can sense food stuck in the gravel, but can't get down to it.  First they will lose their barbels and then they may not be able to feed at all, especially as the undergravel filter will be constantly pulling their food away from them.

 

[robertsmith50]

Ok, that's a start. I should mention however that I have been doing the same thing for the past 14 years with NO problems, and my Corys have been the most trouble free of them all. Of those that have died, some where at least 8 years old, some a couple years, and a few I've had for a month or so. The set up I had before was an 80 gal with only an undergravel for 7 years, and then a canister only for the next 7. I will definitely lower the temp although it has never been an issue. I will also increase my water changes and discontinue the use of the stress coat. I have used it in the past, but have definitely been using it more lately because I could afford it. And as far as stuff building up in the gravel, it is still pretty clean as it's only been 7 weeks. Something has changed over the last 2 weeks, and I just can't imagine what it could be. I may shut down the undergravel filter and see what happens. The canister filter should be able to handle the ammonia by now.
Well, I will try a few things based on your recommendations and see what happens. Oh, I should say that I have been turning off the powerheads at feeding time and leaving them off for 15-20 minutes.

 

[Byron]

Diagnosing disease or related issues is the most difficult aspect of this hobby.  Many various symptoms can be linked to a number of factors.  Which is why we always ask so many questions.
 
Stress is the cause of 95% of all fish disease, so lessening stress is clearly a preventive measure, and my earlier suggestions are relevant here.  Fish under any level of stress, from something as basic as moving them from one tank to another, are in a weakened state.  But as for the specific issue killing the fish, I am thinking even more that it is a nitrifying (cycling) issue, as this tank is only 7 weeks old.  Which bacterial supplement did you use?  How many fish went in this tank at the beginning?
 
Any chance of something else getting in the water?

 

[Fishmanic]

As others have stated, lower temp to around 76 F.  I personally would do away with the undergravel filter and use a python siphon device to change out half the water once a week and clean the gravel thoroughly while siphoning.  
 
You should considering changing the substrate to sand.  Some use play sand but I find pool filter sand is cleaner and works and looks great.
 
  When refilling tank, just use dechorinator, not stress coat,  in the amount suitable for total gallonage of the tank and you can add it to the tank directly and then using the python hose ,  use the strong stream of water to stir up the dechlorinator.  Be sure temp of incoming water is very close to tank temp.  Keep a close eye on nitrites and ammonia and if higher than 0, change water more frequently till it goes back to 0.

 

[robertsmith50]

Well, I lot what I think was the last cory today. All these ideas are worth considering, but I keep coming back to the same thing. I have been keeping fish for about 38 years and have for the most part done it the same way. The only difference is the addition of air and using the stress coat more often. I will definitely change water more and I am going to discontinue use of stress coat and lower the temp, but as far as changing substrate, this type of gravel has never been a problem. I do agree that sand would probably not collect as much gunk, but I finally got my lighting (and reflection off the substrate) just right with blue gravel, 2 blue tubes, and 2 white tubes. The color is exactly what I want, very natural looking and showing absolutely beautiful color in the fish... even the glo-fish. They are swimming in what looks like natural light yet they still glow brightly.
My water does start to yellow within a week and a half after a water change, so I guess that's a sign that it does need more frequent changes but again... that has ALWAYS happened.
 
I am also considering something new. tell me what you think. Running the undergravel filter backwards. I got the idea from an article I read many years ago but have never tried it. Put a water pump on top of the up lift tube to push water down under the filter aso the water is moving up through the gravel and thereby keeping the gravel clean. The only drawback is that the oxygen is used up by the bacteria and then delivered to the bottom of the tank instead of the top. But I have plenty of oxygenating going on in the tank to compensate for that.
 
If that doesn't work, I will just shut it off and leave it in place.

 

[robertsmith50]

I also have not identified the white/gray fluffy sludge that is floating in the tank. There is an awful lot of it. It's too big to come in with the air through the air pumps. Is it possibly some kind of mold that is poisonous for the fish? Weird.

 

[BaylorPerez]

that sounds like leftover fish feces and food that had turned into sludge that can be dangerous to fish if not taken care of. i would suggest any that comes up i would clean out immediately, and when you buy a gravel siphon(python siphon) clean all of the gravel you have, this way no sludge can build up and pop onto the water to become visible.
.
 
Also my cory( i say cory as i have 1 ) has done fine after adding stress coat, it helps from what i can tell and with the cory temperature, i keep my tank at around 76/77 and he/she is very active. liking it in my 20/22 gall tank  

 

[robertsmith50]

Kewl, I will cut back on the food as well. Also, the last couple corys were swimming at about mid tank and resting on the decotative "logs" like they knew the gravel is dangerous.
Another thing to keep in mind is that this happened all of the sudden. One day they were fine, the next day they started dying... and continued dying. Something like new fish, or a change in tap water. Something that happened suddenly.

 

[Byron]

Diagnosing fish problems is the most difficult aspect of this hobby.  There can be so many causes for a symptom, and frequently one can only find the true cause by examining and ruling out the possibles one by one.  Some of the issues I and others have identified here will add stress, I can guarantee it, and stress is the cause of 95% of all fish disease because stress weakens the fish, and the immune system is one of the first processes to be so weakened.  I am not suggesting that any one issue identified will cause corys to die, but the more "undesirables" there are, the more likely fish will fall victim to something that they would otherwise fight off.  We also have no idea if these fish brought some disease in with them, internally.
 
I would however like to comment on a couple of things you have mentioned.  And by the way, I have 12 years more on you (I'm 65) and have been keeping and breeding corys for many years.
 

I will definitely change water more and I am going to discontinue use of stress coat and lower the temp,
 
My water does start to yellow within a week and a half after a water change, so I guess that's a sign that it does need more frequent changes but again... that has ALWAYS happened.
 

 
Water changes are frequently misunderstood.  There is "stuff" accumulating in the water that no filter can deal with, and can only be removed by water changes.  The more water that is changed, the healthier will be the fish.  Once a week is minimum for frequency.  This is especially crucial for corys, as they are very sensitive to water quality and cannot tolerate ammonia, nitrite or high nitrates.  The fact that something has apparently worked for x number of years does not mean there may not be issues, or that things could not be better.  I don't know the number of fish in your tanks over the years, which species, or many other factors that all apply.  I only know without question that water changes do keep fish healthier, and they are the single most important aspect of fish maintenance.
 
As for substances like StressCoat...at the very least these are chemicals added to the water, and they thus end up inside the fish.  There is increasing evidence of likely gill problems with aloe vera, but aside from this, the substance is being taken into the fish by osmosis through the cells, and entering the bloodstream and internal organs.  None of this is natural, in any sense of the term.  And corys are especially sensitive to chemicals and substances in the water.
 

but as far as changing substrate, this type of gravel has never been a problem. I do agree that sand would probably not collect as much gunk,
 
I am also considering something new. tell me what you think. Running the undergravel filter backwards. I got the idea from an article I read many years ago but have never tried it. Put a water pump on top of the up lift tube to push water down under the filter aso the water is moving up through the gravel and thereby keeping the gravel clean. The only drawback is that the oxygen is used up by the bacteria and then delivered to the bottom of the tank instead of the top. But I have plenty of oxygenating going on in the tank to compensate for that.
 
 
If that doesn't work, I will just shut it off and leave it in place.
 

 
Sand is without question better for corys.  For one thing, they have a natural need to sift the substrate through their gills, looking for food.  It is one of the joys of keeping corys to watch them upend themselves, with half their head buried into the sand.  They cannot sift gravel through their gills.  I used to have fine gravel substrates, with corys, until I changed to sand a few years ago, and wish I had done it long ago.  However, this alone is not likely to cause cory deaths.
 
As for the reverse flow undergravel filter, no, this is not at all a good idea.  Normal undergravel filtration can work, if one is diligent to remove the gunk from under the filter plate regularly.  Reversing the flow is not only un-natural but contrary to the natural bacterial processes that occur, or should occur, in the substrate.  The substrate is the single most important part of an aquarium.  There is a host of different types of bacteria that are essential to a healthy environment in the aquarium, far more important than any filter.  You can have a healthy aquarium without a filter, but you need a substrate (long-term).  Water naturally lowers through the substrate, where the bacterial processes warm it so that it then rises back up and into the aquarium.  This brings nutrients to plant roots too.
 
If you decide to discontinue your undergravel, you must tear the tank down and remove it and clean the substrate.  Just shutting off the UG is very dangerous, and the aerobic bacteria living down there, increased because of the UG filtration, will die off and cause terrible pollution.
 
Let nature do most of the work for you.  It is much easier and safer.
 
Byron.

 

[robertsmith50]

Thanks for the info Byron. AS far as having alot of years keeping fish, I just take it all with a grain of salt. When I ask ten people for opinions, I usually get ten different answers. For instance, water changes. Everyone now days say more is better. But ten years ago when I asked the same thing, they said at most once a month and even then no more than 1/2 to 3/4 because more would stress the fish. I could offer example after example, but no need.
 
The problem has been solved. The build up of gunk in the gravel was incredible. Nothing but poisonous sludge. I have clearly been over feeding them and the undergravel filter was suckingit all down. I threw the sludge under the microscope and discovered that the sludge was being held together by dog hair. Two of my dogs shed pretty bad and it's always in the air. My computer fills up with the stuff every week and has to be blown out. Anyway, once the hair mixed with the gunk and food the filter couldn't suck it up.
 
Anyway, I had to pull everything out and vacuum the heck out of the gravel. What a mess. I pulled the undergravel out, and will increase gravel vacuuming and have lowered the temp. As long as the canister filter can keep up with the ammonia, I should be ok.
 
So thanks for all the info and help.

 

[robertsmith50]

Hello all. Just wanted to say thanks again. The tank is still without its decor so I can keep track of all the fishes. I was pleased to discover that three of my favorite Corys were still alive. I added 4 new albino Corys to the tank 2 days ago and they are all doing well. The ammonia levels are still zero even without the under gravel filter. I can't say enough about how much I like this new canister filter. It's a Hydor professional 600 canister with no bypass. It gets the water much clearer than the tap water I start off with. Absolutely crystal clear. It also has 5 trays instead of 4 like most.
So anyway... Thanks again.