I do agree that bioballs are not necessarily the culprit of becoming famed nitrate factories. The only problem is that they are a pain in the wazoo to clean out when they get packed with detritus. To me, I found it much easier to clean a wet/dry with live rock in it than one with bioballs.
Ishmael(sp?) you can get epdm or marine grade at HD or Lowes, goodiebag, aka Brad from Aquarium Design has them in his sump, I personally don't have any baffles, I have live rocked packed in every square inch of water that is my sump.
Another good place to read up on sumps is www.melevsreef.com
I personally would wait on adding any other fish until you get a bigger, better skimmer, especially if you want to add corals. Granted softies are somewhat more tolerant of poorer water quality, but I do not promote poor water quality by any stretch of the means. Especially with a hippo tang in there.
I have a 29 gallon tank as my wannabe sump. I just took the hose from the overflow box and put it in the 29. It just hangs in there. I put a EuroReef skimmer in there, about 60 lbs of sand, and about 50 pounds of rock to occupy the rest of the space. I buried my mag5 return in the rocks to keep microbubbles from the skimmer from getting in it. I also took the inside of some swim trunks and covered all inlets of my pumps to prevent any of my clean up crew getting stuck in either of those pumps.
I have my heater in there as well, but it only turns on at 75 degrees. My water pretty much stays at 76 constant, so the ebo-jager only turns on to prevent a catastrophe.
Keep an eye on your nitrates, and keep doing about 15-20% water changes to air on the side of caution. If you do a search, there is plenty of info about skimmers on this website. If you want an inexpensive skimmer that is worth it's weight in gold, try an Octopus Skimmer. Aquarium Designs sells them. One for your setup will run you roughly 100 dollars, but you'll need a simple sump like mine for it. You can come by and check mine out if you'd like, just let me know!