I have a fairly new 40g fish only tank (been running about a month now with a couple damsels and a small maroon clown) and all seems to be going well, but I've heard conflicting things about protein skimmers. Some people swear by them and say they are totally necessary while others say not to waste my money. I don't have a sump and I'm running an Eheim cannister filter now. Do I need a skimmer?