please help! my Colombian shark also known as the black fin shark won't eat! he has been lying down and only swims around a occasionally. Hes about 4-5 in. he has one other tank mate, another Columbian shark. I bought him a few days ago he is healthy and happy and is swimming around eating normally and both look to be very healthy. I have had this shark for a few months and he has been fine. I am going to test the water parameters and write an update in a few hours I will also tried to load a picture of him. he is currently in a 20 gallon tank and yes I know he will need a much bigger tank. I am looking into a 300 gallon. sorry if this sounds rude but please don't tell me I need to send them back to the local fish store or something because I have done lots of research on these fish and know how to take care of them well. I just need to figure out why my older Columbian shark won't eat:'( I am also planning to add a third shark since I know they are schooling fish. I currently feed both fish wardleys shrimp pellets(sinking) but plan to expand there diet. please help!