yeah, that's a huge bio load for a 29! i cant believe the cowfish and hippo havent outgrown that tank (assuming they've been in there a year). anyways, there are plenty of people that run skimmerless systems and have great success. either way, since spanko pretty much answered everything else, i'll add my two cents on the rest...
aside from the size of your tank and the kind of fish you have: absolutely do not stress the cowfish out, they can release a toxin into the water that will wipe out the entire tank, including the cowfish itself.
not that you asked, but because you commented on not knowing how skimmers work:
there are several different types of skimmers that mix air-bubbles and water in different ways. essentially, a skimmer creates air bubbles that come into contact w/ water in the reaction chamber. inorganic wastes in the water stick to the bubbles thus creating a foam that rises into the collection cup which eventually turns back into a tasty green liquid. the more bubbles, the better the skimmer will do its job. the longer said bubbles are in contact w/ water in reaction chamber, the more waste will adhere to them, the better the skimmer will do its job.
like i said before, plenty of people opt not to rock a skimmer, but i swear by them. good luck with your trates. i think the best way to lower your nitrates would be to get a bigger tank.
