Sorry to hear that silent_rock_faery
I also don't think the black stomach was from ammonia poisoning, they can turn a more orange colour when older I believe. If the fry were just born, they wouldn't have affected the ammonia levels to any degree. Other possibilities could have been from improper diet or lack of food, fungal or bacteria infection from the gravel...perhaps he even swallowed some of the fry that were hiding in the gravel (just a silly thought).
Dano! I think Gyrinocheilus Aymoniery are a type of albino sucking catfish from the chinese algae eater family. They seem to be very popular in Aust. and seem to be in nearly all LFS' here. They are nice looking, but can be very aggressive when a bit older.