I only asked you if soak the krill first cause dats of that size can sometimes choke on unsoaked fdk. This could cause an infection. Not saying this is what's going on here. Just trying to come with something. And yes waterquality could have caused this which can cause a redlike ulcer. But you said he was eating, which doesn't usually go with poor water quality and ulcers. If this fish is eating normal and acting as normal as a healthy dat should, I wouldn't worry too much. fdk and bloodworms really aren't gonna provide all the necessary growth inducers and disease preventative ingrediants vs a pellet or wholefish
