I had a 20 gallons running few years ago and realize now that I have been very lucky because it basically ran itself. It has been empty for the last 2 years and I just started back in January 2012. I have bought the same kind of fish I have before as of silver tipped sharks and bala sharks. My daughter thought rainbow sharks were pretty so we ended up buying 2 of each thinking they probably would not all make it. Rainbow sharks didn't last very long. I pull one out because it was chasing all the other ones away and the other rainbow jumped in the filter and got stuck. It has been about 4 months now and I lost both of my balas and one silver tipped... I just got my water tested today and everything came back OK. The fishes start swimming weird for a day or two and are becoming a lighter shade of gray and we can see through them right before they die. The lady who helped me ( at pet smart... ) didn't really know what to do and kept telling me it is probably a bacterial problem going on in the tank. And suggest to do a 50% water change and add more salt ( 2 tablespoons)... That's it... I am also noticing some brown growth on the side as well as on the rocks and decorations. Is that brown algae? How do I get ride of that? Bigger filter? Temperature change? Has it is now my temp is always around 82. Is it too hot? How much salt should I add this tank and how often? I did buy some plant lately and they seem to be doing OK. I don't know what to do anymore and sure don't want to buy other fishes if they are going to die :-( Can someone help me?