Hi, could anyone tel me what sort of snails a freshwater green black spotted puffer fish can eat? I feed him on frozen blood worms which he loves, and also occasionaly a cooked scrimp. Petsmart say they can't get any snails for a while, don't know why. Also, I have Penguin power filter with bio wheel, I know you don't do anything to the bio wheel as regards cleaning, but what about the filter? it gets really gunky and I have , at water changes, swished it around the old tank water in a bucket, but its still gross, so is it ok to change it? after I rinse the new cartidge in old tank water? will this mess uop the good bacteria? or won't it matter cos of the good bacteria on the bio wheel I am a little confused about that, that's so much for any advice.