in my 10g i have 2 clowns and 1 watchmen goby. i have had it this way for about 4 months and no problems but there are a few extra steps i take to make sure im not overloading the tank. heres what i do:
test weekly(compaired to my every other week on my 55g)
2 water changes a week. (normally half gallon)
very little feeding (just enought to keep the clowns fed and no extra, little bit but not much)
i run a AC70 modded to fuge to keep trates down
i also run a carbon filter in it once a month for a week
so far everything seems to be ok. the clowns seem to love it in there. lots of swimming and what not. i plan on getting them a frogspawn in the future to see what really happens. my real goal was to see if i can get them to reproduce. and then after that i will probly release them back into the 55g. but until then they seem to like it mostly by themselfs.
good luck