Forgive me in advance if this topic has already been discussed. I'm fairly new to goldfish breeding but I have a lot of tank space and time to mess around with fish so I pretty much jumped off the deep end with breeding. I have a few batches of fry right now that are all under a month old. I have been keeping them in 2.5 gal tanks with the thought of moving them once they grow more. With most batches I've probably had anywhere from 40-100 fry. Most of the fry are doing well but I have one batch that seems to be dying off more so than the other batches. I have had this problem with one other batch in the past (probably not the same parents but the female could be the same, first batch was a mixed breeding of a bunch of fish in a 150 gal vat, this batch is the product of female nymph (chubby, single tail), a male oranda and a male fantail). Anyways both the previous fail batch and this current batch that is going downhill fast have developed this bubble underneath them that I haven't seen develop in any of my other batches of fry. Sorry, couldn't figure out how to post the pic here so here is the link Basically my question is, Is this normal or is this bubble some sort of developmental error? And could this be causing the high (100% in my first batch) mortality rate that I'm seeing or should I be looking for other potential causes. Other info: I've been feeding very fine dry fry food every so often but have primarily been feeding baby brine shrimp that I purchased in a jar and keep in the fridge. This week I started hatching brine shrimp and feeding them live to see if that would help. I've been feeding as needed (whenever their stomachs have shrunk back down from the last feeding which equals about 2-3 times daily). I've also been doing ~25% water changes 3 times a week a with that trying to make sure I get any debris off the bottom. The water I've been using to fill after a water change has been conditioned and sits in an empty tank with an airstone until needed. All my tanks are at room temp which stays constant around 71. Hopefully this info helps. Any advice you can give me would be greatly appreciated.