I have a 40 gallon tank with cichilids only, and I went to change my filter and do a water change and the filter was covered in little black worms. Most still alive. What is this? Recently I did buy some fish from a small fish store that didn't have the most cleanest tanks. do you think I got them from there? Also I have a 55 gallon tank with bala shark, red tail black shark, golden gourami, green cory catfish, a pictus catfish, and chinese algae eater. In this tank the chinese algae eaters are the new ones also in this tank the worms have been found but not as many. I put a parasite chemical to try to get rid of them before they harm my fish. Can anyone help?