I've been trying to keep my guppies alive... first one died right after coming home from the store, then my tank exploded at a seam and I was only able to save two. These two were happy for a few months (about 6), until one showed signs of stress, and translucent poop. Before I could react, he was gone. Now left with one, he seemed really lonely. I brought home 3 more guppies for company. All was well for a few weeks, until now -- I'm looking at the blue one from the original group, and he seems extremely bloated. I'm not sure what to do? I am attaching a picture to give you guys an idea. Before the guppies, I had two beautiful goldfish. One passed away rather quickly, with some some intestinal disease, the other one was fine until I added a second filter to the tank, using the same hardware that had been in the sick tank with the dying goldfish. I had been leaving it out dry for a few months, ran it in a bleach solution, left it out for a while longer -- as soon as it was there, my second fish got sick and died. Could this be something that is still in my tank? What do I do, in this case? Water parameters are stable, with no Nitrates, no Nitrites and low Nitrates. temperature is at 78 F and Ph is at 7.6. There seems to be plenty ocigen -- both filters waterfalls, and an air stone. Undergravel filter + a Marineland biowheel filter. Some plants (both silk and real), 2 moss balls, a few sakura red shrimps and 3 nerites in my tank.