LauraFrog
Fish Gatherer
Sounds like an abort, probably due to recent move. Euthanise the ones that are rolled up in balls. They are undeveloped and will never grow into adult fish but may suffer and try to move without inflating their swim bladders for several hours before they die. Fry with twisted or bent tails will not be able to swim either, we call them taildraggers. They have to be euthanised as well. I have never had a brood without at least one or two taildraggers or fry that failed to unroll. The proportion of deformed or half developed fry increases if the female is very young (first few broods are only a few fry, she may not even look pregnant - maybe yours is young, how big is she?) very old, hasn't mated for a long time or there is a lot of inbreeding in the line.