PlanetCatfish.com

Sorry to hear that.

There are many things that can go wrong with internal organs, including swimming bladder. If the fish never had any problems or illnesses before, with the bladder or otherwise, then it is even harder to be sure. Swimming bladders can be affected by both parasites and bacteria.

Healthy and balanced diet is always one key to long term success.

How old was the fish? Perhaps it passed from old age. I don't think bullheads are known to have a long lifespan, for some reason about 10 years is coming up in my memory... but this could be for the lack of more data.

Moreover, mutations do not occur one at a time but in bunches. Since your catfish was a mutant (as I naively or ignorantly assume all color morphs are, which deviate from the normal color), it must have had other deviations in its genetic makeup in addition to those controlling pigmentation. Most usually mutants exhibit a shortened lifespan and weaker overall health.

he was 4 years old.
For not reproduce error, which diet is recommanded ?
He eat a wafers tropical carnivores and fish.

What is the ingredient list of the wafers?
What fish? Live, fresh, or frozen/thawed? What species? If it was stored, how was it stored?

For wafers: https://www.aquaristikshop.com/aquarist ... re/172465/
The fish are frozen (Atherina boyeri) and are stored in my freezer.

I don't see any red flags in the diet. It seems pretty good. Smelt and decent quality, balanced and complete dry feed.

I maintain my initial suspicion that the chances are high that your fish are subjected to persistent low levels of ammonia and nitrite. 100 gallons is a small volume of water for your apparently large fish.

Let me ask you this. The very crude rule of thumb for a stocking level of a fish tank states that one better stay under 1 cubic inch of fish body volume per 1 gallon of water. Please, eyeball and estimate - are you in violation of this rule?

Say, if your bullhead, which is a stocky fish, was on average 10" long, 2" wide, and 2" tall, that would already come to 40 cubic inches, that is roughly halfway to the maximum recommended. And you also have a carp and oscars in there of the size you haven't mentioned yet.

One needs a large enough volume of water for what's called instant dilution of the ammonia and nitrite toxins to the levels below readable by a liquid test kit (BTW, I have never met with a nitrite test showing 0.05 ppm because our best kit the API starts out at 0.25 ppm as the first readable number, so I am not sure how to interpret your test result of 0.05 ppm).

In low volume of water, fish are quite prone to the brown blood disease, which you can read up on.

My tank mesure 150 cm x 40 cm x 60cm (400 liters net, 450 liters brut)
Oscars are 3" and carp 11" but the carp went go to the pond.
I find this is a sufficient volume for black bullhead.

The cubic inch Victor mentioned is 15,625 cubic centimeter. Assuming a fish weighing the same as the water it replaces (fish generally weigh a little bit more, but not much) Victor advises 4 grams of fisdh a liter.

The oscas would weigh 50 grams each, the carp 700. That is, there was room for some 800 grams of fish left. From the look on the picture I guess the fish to weigh a kilo. Perhaps more.

Now I think there is a difference between rules of thumb in the USA and in Europe. These could be both true, in America I understand people change more water, pump more, and yes that allows one a bit more fish.

However, if you keep your fish the European way, with less waterchanging and so on, the European norms should be used. I myself aim at 3 gram per liter. For regular fish. Very sensitive ones less, rather insensitive ones can be kept with more.

I'm afraid the tank was too small.

Thank you Bas for this. Appreciate it. Didn't realize the regional differences in fish keeping. Just thought I'd again stress that 1 cu inch per gallon is the max, that is pushing it and leaving no room for error, which is not a good thing and not deemed a "good, humane practice" by most.

*******

OK, Kiwidu. Thank you for that too.

I wish information like this, and the rest we fished out of you one piece at a time as a result of this thread, would be provided in the original post to eliminate unneeded and wasteful guessing.

Providing good, adequate info is neglected in almost every post asking a health-related question. Water parameters must be cited, and how they are measured, the tank must be described, the tank mates, their interactions, filtration, aeration, whether the fish are wild caught, dewormed or not, treated against other parasites or not, prior health history of fish, of tank mates, these are all a must, and photos of the entire tank and closeups of the fish are always useful.

Anyhow, my suspicion about overstock may be off then... until we get to see the ammonia test result. Also, when all these fish lived together, the tank might have been pretty heavily stocked by the rule of thumb.

Dealing with rational explanations, I would have to fall back on the mutant hypothesis, that is that their lifespan and health are compromised in a variable way just as their appearance.

Of course, there could be many other reasons, almost all indecipherable by a layman and hobbyist, many of which having to do with the origin of the bullhead and its tank mates and their pathogen cultures they came with or the pathogen cultures they had acquired before coming to you and in your care too. This is a black box with the Schrodinger cat that may or may not be in there...

the test of ammonia can see is <005 mg/l (ppm) so it is good

Excellent.

Granted we don't know what the ammonia was at when your tank had been fully stocked with the bullhead and the carp and the oscars, albeit the latter were small. Your ammonia might have been elevated and you'd not know if you never checked and this still remains a possibility that did your bullhead in. We can't discard it. We'll never know.