Hi, I have a 55 gallon aquarium with some fingerling koi in it until I get my pond up and running. The only thing I've noticed is that is smells, it smells like something is rotting. I was thinking algae? Is there anything I can do to get rid of the smell???????? I was thinking of a bottom feeder sucker fish to get rid of all the algae? Would he give parasites to my koi?