Ok, y'all know those feeding blocks that are sold everywhere and are meant for vacation. DON'T USE THEM. If you are going to be gone for a week or less, your fish will be fine anyway. But I put one in my 55g tank with 4 angels, some tetras, a ton of guppies, and a pleco. And when I got back, ammonia was at like .25 ppm. (Really high) And it killed one of my angels. So just a warning to people, even if you just have one sitting around, don't use it. This was like Nov. but I thought I might be useful to some people on here.