I can't count the amount of fish I lost over the years. There was at least a goldfish a year when I was younger, a few plecos. Then when I got my own tanks, I lost Angel fish, Mollies, Frogs, Platys, plecos, silver dollars (these were the only ones who actually survived) and my Betta Joey. Years later I decided to pick up the trade again and do it a lot slower than when I was younger. Now I QT my fish, now I know what fish get along and what fish need certain types of waters etc. I have no advice other than just research and ask questions :)