I have a very small 16 litre tank, yes I know it is small, and I had a small goldfish in it which died this morning. I rescued this goldfish from a junkies house last year, it had been in a very very small glass tank in filthy conditions and had not been fed for two months. Anyway I bought this 16 litre tank and everything was fine until today. I now want to put some small tropical fish in it like tetras or something else, please advise, how many can I have, I know I can't have very many but am asking advice because I know nothing about tropical fish. I know I will have to buy a heater. This tank sits on my kitchen worktop. Have cleaned out the tank, pump etc very thoroughly so what do I do next? Thanks in advance. I was really upset this morning when I found the poor thing.