Well,this morning I found that one of my six bloodfiin tetras was swimming upside down! Hopefully,it is not a bacterical infection or a fugus injection. I removed the poor tetra into a styrofoam cup and replace the top half of the aquarium water with new water. In addition,if the tetra is not right correctly due to constipation,is there a laxative that I can feed the tetra besides a pea? Since I do not have any at home.