Is the brown crap slimy and like a carpet? If so, then it's cyano, or red slime algae. Is it dusty and rust-colored? If so, then it's diatoms. Diatoms will come and go on their own, and as your tank matures, you will get them less often. With slime algae, you have to be proactive in getting rid of it, i.e. adding more circulation, doing more water changes, feeding less, etc. It's a bitch to get rid of. I've been battling cyano in my tank for a month now.
For a cleaner crew, I would start with maybe 30 snails/crabs TOTAL. If you find you need more, then you can add more later. But like Yote said, a lot of people buy huge cleaner crews, then they all starve to death and pollute the tank.
I agree with Yote on the pygmy angel -- they are known to take out corals. Buy at your own risk. I, personally, would not put one in my tank.