Disease or aggression killing fish?

[Jay Hemdal Verified Community Expert]

Funnily enough did some digging on it possibly being brook so glad to have that corroborated.


Assuming as per the above comment, since tank is now empty of fish, I won't need to dose anything, just several major water changes and keep it fishless for 45-60+ days to eradicate brook remnants in the system?

Also, likely that brook was introduced via the latest fish additions three months or so ago or just something lurking for a long time?

Brooklynella has direct development, with no resting stage. The resting stage is what draws out the fallow period in aquariums (ich or velvet tomonts, fluke eggs, etc.) I suspect that true Brooklynella dies out fairly rapidly, but I don't push the issue because of the risk of misdiagnosis.