Corydoras Aeneus Surfacing and Death

[mark4785]

In the past 2 months all of my Corydoras Aeneus have been showing some worrying symptoms. Some of them have receding tail fins or frayed tail fins and one or two keep surfacing for gaseous oxygen as though their gills are incapable of taking up dissolved oxygen in the water.

These symptoms are then followed by extreme paleness and death.

I presently have another species of Corydoras in the aquarium that appear to have slight barbel rot but which are not dying.

I'm a little concerned as to why this is happening given that the water quality is excellent with 0 ppm of ammonia and nitrite, a pH of 6.5 and a mixed diet of blood worms and Tetra Tabs (both the high protein and high vegetable matter content).

The only thing I can think of that may have caused the fin/barbel rot is the fact that a piece of frozen fish that is provided with frozen discus food mix is too big to be consumed by my top dweller's and so some bits may have become rotten on the base of the tank. I do know that Corydoras are susceptible to fin rot issues if they consume rotten food or decaying fish. I have since ensured that these inedible pieces never enter the aquarium but I'm stumped as to why the rot and deaths are continuing.

The aquarium has been treated with Seachem Kanaplex which is now being followed up with a course of Waterlife Myaxin. These both treat bacterial infections.

Is there anything else I can do?

 

[Byron]

There are some possible causes for the described condition. What other fish aside from various corys are in this aquarium? What is the GH of the source water? What is the nitrate level? What is the temperature? What is the substrate composed of? How frequent and what volume are water changes, and do you vacuum the substrate during these?

The foods are not the reason for the problems, but good nutrition will help fish get through problems and keep them healthier. I would change the corys diet a bit...actually, a lot. Bloodworms are not a good staple food; mine get these once a week as a treat after they have tolerated the water change. As daily foods, shrimp pellets are good (Omega One make these, as do other manufacturers, but Omega One doesn't have "junk" binders in their shrimp pellets), and Omega One's Veggie Rounds are a good way to get some plant matter in the fish; while corys do not generally eat plant matter or algae, the "veggie" is good for their intestines and digestion (applies to all fish). I don't know what is in the Tetra Tabs, they may be fine as another alternative food. A variety of good prepared foods is advisable.

When I have the answers to the above questions I should be able to offer more. A bacterial problem is not ruled out, but I am doubtful. As for the products used, the Kanaplex is relatively safe, though it may not have any effect on the issue, but I have used it with corys and similar fish with no adverse effects. The Waterlife Myaxin I don't know, and I cannot find the ingredients anywhere...does it say on the label? This product is allegedly so broad in its treatment that I would question its effectiveness for almost anything. I wouldn't dose either of these again, until we have a better understanding of the issue, and if either seems the best treatment.

Byron.

 

[mark4785]

There are some possible causes for the described condition. What other fish aside from various corys are in this aquarium? What is the GH of the source water? What is the nitrate level? What is the temperature? What is the substrate composed of? How frequent and what volume are water changes, and do you vacuum the substrate during these?

The foods are not the reason for the problems, but good nutrition will help fish get through problems and keep them healthier. I would change the corys diet a bit...actually, a lot. Bloodworms are not a good staple food; mine get these once a week as a treat after they have tolerated the water change. As daily foods, shrimp pellets are good (Omega One make these, as do other manufacturers, but Omega One doesn't have "junk" binders in their shrimp pellets), and Omega One's Veggie Rounds are a good way to get some plant matter in the fish; while corys do not generally eat plant matter or algae, the "veggie" is good for their intestines and digestion (applies to all fish). I don't know what is in the Tetra Tabs, they may be fine as another alternative food. A variety of good prepared foods is advisable.

When I have the answers to the above questions I should be able to offer more. A bacterial problem is not ruled out, but I am doubtful. As for the products used, the Kanaplex is relatively safe, though it may not have any effect on the issue, but I have used it with corys and similar fish with no adverse effects. The Waterlife Myaxin I don't know, and I cannot find the ingredients anywhere...does it say on the label? This product is allegedly so broad in its treatment that I would question its effectiveness for almost anything. I wouldn't dose either of these again, until we have a better understanding of the issue, and if either seems the best treatment.

Byron.

Hi Byron,

The other fish include 2x Discus, 2x GBR's and 2x Ottocinclus. The GH value is 6dH from the tap and the Nitrate level, in the aquarium, is 20 ppm. Temperature is 28 degrees (has been 28 degrees C for 7 years and normally causes no issue for Cory's) and it is a bare-bottom aquarium. Water changes are weekly with 40% of the water and any detritus (there is little detritus) being removed with a siphon.

Blood worms are not the staple diet of the Cory's. They have 1x Tetra Tabimin tab (which has the shrimp content you mentioned) and 1x Tetra Veggie Tab each day. They will inevitably consume some blood worms though since the Discus are fed these daily since it is a constituent of their frozen mixed food.

I was under the impression that fin rot and frayed fins were purely a result of a bacterial infection? They are not being nipped or scuffing themselves.

 

[Byron]

Fin degeneration can be due to nipping as you mention [you're sure the rams haven't been?...this is not uncommon], and also bacterial, fungal, pH, nitrates, ammonia/nitrite, other toxins in the water including additives...almost anything. This is why one has to try and sort out the improbable in order to arrive at the more probable, and before treatment as this can make things even worse.

If the upper fish are not showing these symptoms, it is probably less likely to be bacterial, though that is not a certainty. From what you've mentioned, I would first off suggest the temperature is too high for Corydoras aeneus; I realize it may only be a degree or two above the upper limit of most suggested ranges (SF has 21-27C) but this can be serious to a fish. A fish's metabolism is driven primarily by temperature, since they are ectotherms, so warmer or cooler than the species "prefers" can significantly alter the functioning of its internal systems over time. I see no issues with GH and pH here. I realize the warmth is essential for the discus and rams, so a better cory species would be C. sterbai, commonly seen with discus and wild-caught angelfish (which also need the warmth,unlike their commercially-raised cousins), or one of the other few species that can manage with higher temperatures. Now I admit the temperature alone is not likely the issue here, but it is one factor adding stress to the fish, and that adds up. It might also contribute to a bacterial problem if there is one.

Bloodworms are also not the issue, though again this is pushing the envelope. No fish should have daily feedings of bloodworms, they are not that nutritional and they are detrimental. I can never remember if fat is the issue, but I know something in worms is, and they should be fed sparingly. Once a week for any fish. I don't want to get involved in discus nutrition, but according to Jack Wattley, a good prepared food is sufficient and sometimes preferable, and few know more about discus than he does.

The bare substrate is not good, for any fish frankly, but especially for cories. This may be a factor in the issue. Corys must have sand to sift through their gills. Barbel degeneration may well be linked to this lack of a substrate; sand hosts an army of good bacteria, and these are crucial for substrate level fish but also for the biological system of the aquarium generally.

I would up the volume of the water changes, to 50-60% weekly (at one time is more effective). Discus breeders usually suggest at least twice weekly, but again I won't get bogged down there. I would also mention that breeders who do use bare-bottom often change the water more than once every day, up to 90% of it. Admittedly they are raising fry in these tanks, and that makes a big difference. But your substrate is the single most important part of an aquarium housing fish, much more than the filter can be.

I'll end by saying that things may have seemed fine for 7 years, but we cannot possible say that with confidence. The corys are definitely having a rough time, and all of these factors contribute to fish health.

Byron.

 

[mark4785]

Well with Cory's i've been told that they don't fair too well with course substrate, which I don't have or use. Glass doesn't generate much friction so I don't see it being the cause of barbel loss, especially since only 3 of the 8 Corydoras have receding barbels. The 3 corydoras fish with the receding barbels are the suggested Sterbai species so no matter the species and temperature, there is a disease present.

As said, bloodworms are not the staple diet of the Corydoras. I use a frozen product named BCUK Discus Food which comprises beef heart, bloodworm, gammarus and vegetable food. This is fed daily to the Discus on the advice of the previous owner and they thrive on it. Some small pieces of this food may get consumed by the Cory's but not an awful lot. The Cory's main diet is the sinking tabular food that I mentioned.

I'm just going to take the view that the 'inedible' fragments of BCUK Discus Food that have reached the base of the tank have become rotten and infested with bacteria which has then been consumed by the Cory's and has resulted in a bacterial infection unless somebody has any other ideas. This is the only plausible explanation that I can personally think of and it also makes sense to me given a previous experience I had where a Neon Tetra I had died and on that occasion the Cory's consumed some of its rotting flesh and they ended up with a Pop-eye bacterial infection 1-2 days after.

Given that my ammonia, nitrite (both 0 ppm), pH (6.5) and temperature (28 degrees C) are consistent with what I've run my tanks at over the last 7 years it doesn't resonate with me that these variables could conceivably cause health problems where they have not in the past.

 

[Byron]

I'm just going to take the view that the 'inedible' fragments of BCUK Discus Food that have reached the base of the tank have become rotten and infested with bacteria which has then been consumed by the Cory's and has resulted in a bacterial infection unless somebody has any other ideas. This is the only plausible explanation that I can personally think of and it also makes sense to me given a previous experience I had where a Neon Tetra I had died and on that occasion the Cory's consumed some of its rotting flesh and they ended up with a Pop-eye bacterial infection 1-2 days after.

No fish should come down with pop-eye from eating a dead fish. Unless the disease was present in the dead fish, and this would further depend upon just what it was. Several things can cause "pop-eye." I had a fish with this once and a microbiologist led me through the process.

If you are correct that the corys eating the sunken food is to blame, this supports my position on the need for a substrate. Without a suitable bed for the many species of bacteria essential to a healthy aquarium you are running the risk. I have maintained and spawned many species of wild caught cories over fine gravel and sand for over 20 years and never had these issues.

The lack of adequate water changes--which are inadequate primarily because of the lack of the bacterial bed--only contributes to the problem.

 

[mark4785]

No fish should come down with pop-eye from eating a dead fish. Unless the disease was present in the dead fish, and this would further depend upon just what it was. Several things can cause "pop-eye." I had a fish with this once and a microbiologist led me through the process.

If you are correct that the corys eating the sunken food is to blame, this supports my position on the need for a substrate. Without a suitable bed for the many species of bacteria essential to a healthy aquarium you are running the risk. I have maintained and spawned many species of wild caught cories over fine gravel and sand for over 20 years and never had these issues.

The lack of adequate water changes--which are inadequate primarily because of the lack of the bacterial bed--only contributes to the problem.

Well the Cory's I had in a previous aquarium consumed on a deceased fish and then developed pop-eye. This is what happened; I'm sorry if you disagree with these course of events.

On the topic of substrate, this isn't necessary. I have a pond with no substrate and the fish are happy (and have been happy for 10 years) and so were the Cory's in the aquarium prior to me feeding this BCUK Discus Mix food which is messy and which seems to be getting sucked into the filtration system very easily having observed this last night. This rotting food seems to be contributing to higher bacterial levels which is apparently a causal factor in fin rot (do a quick Google search on the causes of Fin rot and see for yourself).

The absence of substrate would only be a problem if the absence of nitrobacter and nitrosomonas bacteria, which would normally cultivate in a substrate, was causing the ammonia and nitrite to rise which isn't the case here. I chose to have a bare-bottom aquarium as I was told it would be a way of being able to keep the base clean since no detritus would get ingrained into the substrate. This cleanliness is going to plan, however, the BCUK Discus food I mentioned which I thought was all edible in fact has large bits which are inedible and its the inedible bits that I think have become rotten and caused the Cory's to become sick. This would make a lot of sense since the Cory's are the only fish to primarily swim on the base where the inedible bits have sunk.

 

[Byron]

Well the Cory's I had in a previous aquarium consumed on a deceased fish and then developed pop-eye. This is what happened; I'm sorry if you disagree with these course of events.

It is not the sequence I am refuting, but the relationship, as I think I explained previously.

The absence of substrate would only be a problem if the absence of nitrobacter and nitrosomonas bacteria, which would normally cultivate in a substrate, was causing the ammonia and nitrite to rise which isn't the case here. I chose to have a bare-bottom aquarium as I was told it would be a way of being able to keep the base clean since no detritus would get ingrained into the substrate.

This is an incorrect understanding of bacteria and substrate. There are many more species of bacteria than nitrifiers living in the substrate, and they are essential to a healthy aquarium. It is true that in the absence of substrate, some will colonize the filter, but the substrate provides a better bed and without more frequent water changes there is simply no substitute. The detritus getting into the substrate is exactly what you want to feed this important bacteria bed.

You are of the opinion that the initial cory issue is bacterial, and I have not ruled that out by any means. But if it is bacterial, then your lack of a substrate is quite likely a factor in causing it.

 

[mark4785]

I thought I would post an update to this thread because the issue is still persisting.

Although no more Corydoras have died, two of my albino Corydoras Aeneus are surfacing repeatedly. They are spending about 90% of the time taking in air from the surface. All the colour has drained from them and their fins appear shorter as though they are rotting away.

I'm confused as to whether this is bacterial fin rot or gill flukes or both.

I'm also confused as to why my German Blue Rams, Ottocinclus, Neon Tetras and pair of Discus are not suffering at all from the same symptoms. It is just the Albino Cory's that are surfacing until they eventually die from exhaustion.

I do need urgent help with this.

Note: Ammonia and nitrites are still at 0 ppm, pH is around 6.5 and the temperature is 28 degrees C.

Note: Took a closer look at the Albino Cory's and can see that their scales are slightly raised too.

 

[mark4785]

I have just treated the tank with Kusuri Wormer Plus on the basis that I cannot find any source, whether from the internet or in any books, to suggest that bacterial infections cause fish to hang at the surface gulping air in. I just hope I've made the correct treatment decision for the sake of the fish.