Hey! thanks for this. Some good pointers for sure!
What are the parameters of your water change water that you’re adding
Besides the ammonia, nitrite and nitrate, i havent tested much on the tap water. I did confirm that it has no clorine or chloramine, and also checked that is has no phosphates recently because of an issue with black beard algae that i also seem to struggle with. What would you test for in tap water?
What is your stocking density like
It is a 720 liter (190 gal), with 12 fish in it (most of them small though, only 2 that are fairly large, but still just fancy goldfish, no commons). My other tank is 530 lit (140 gal) with 4 fish, but that is mostly a quarantine tank at the moment. Both heavilly filtrated with canister and DIY biological filtration
Are you temperature matching your water change water
To be fair, this could be an issue. I do water changes every 7-10 days, not because the nitrates are high, but mostly to just keep the water fresh (and the alleged hormone production down). Because of the size of the tank, our heater runs out of warm water, so the temps match pretty well to start with, but the last 10-20% may be substatially colder. I havent given it too much attention though, because others that i speak to just pour ice cold water into the tank, and don't think about it (or have any issues). I am pretty certain that all of the nitrogen circle values are fine. I have extreme over filtration, so I am certain that both ammonia and nitrites break down more or less instantly, but more and small water changes could be a way forward (although it would be a lot more work)
A varied diet never hurts
I do experiment with many different pellets. Currently i use two types, but i have had up to 8 different types(!) and suspected some of them to be worsening the issue actually. They also get veggies and artemia/bloodworms. In regards to veggies i give them peas, broccoli and spinnach
Are all your fish the same type from the same stock? It could be a genetic problem.
No and this is why i am mostly concerned. If it was one or two, i could accept it as a genetic prblem. But i have multiple fish from multiple breeders and even more rescues. It does seem like the more extreme body shapes do worse (short bodies, tall backs and small tails seem to have bigger issues that regular fan tails). But i believe that something is causing them to be the first to be attacked by this condition.
If you do have mortality, would you be comfortable dissecting one to look at the swim bladder?
I have had no mortalities, but I have euthanised a few that were really struggling. I wouldn't mind dissecting, but i wouldn't know how or what to look at. The good news is, that i have a vet that would be willing to help, even though she probably whould't know what to look at either. I could even have x-rays taken if needed, but still the vet would have no idea about it. I am fortunate to be in contact vets around me who are honest but willing to help as long as they are sure the fish don't suffer.