Little whilte spirals??!?!

You know you could always add some inexpensive base rock which then will become live rock from the rock you have. Many people put half live and half base rock in their tanks to boost the amount of rock. If your existing live rock is that loaded with bio then adding the base rock should be no problem. Just make sure the rock is suitable for saltwater and away you go. Sand for the bottom doesn't necessarily have to be live aragonite, you can possibly pick up aragonite play sand cheaper and seed it with live sand also. These things will help defray the initial high set up costs. A protein skimmer is important as eels do produce heavy bioloads.........much more than small fish do. Remember read read read and when you think you know something....head back to the books and read some more. This is a learning process believe me.
 
Welcome to AC :D
You've got a decent canister filter on the tank, so even without loads of LR you've got good bio filtration on the tank. A skimmer would be a huge asset as soon as you can get one on the tank; big eaters produce large amounts of waste and a skimmer will help keep water quality in line.
Lots of people keep predators in FO (fish only) tanks, using a filtration method other than LR, I think your little monster will be just fine for now as you slowly add rock. The more LR you add, the more tiny critters will appear and, IMHO, the more balanced and diverse your tank will become - it's amazing, after nearly a year I'm STILL seeing new things on the LR in my 30g.
I agree the white spirals are likely teeny worms, totally harmless filter feeders. The creepy crawlies you're seeing on the glass are probably pods (copepods, amphipods or isopods, there are countless varieties of each, most are harmless/beneficial).
I'd ease up on feeding the hermits, unless they're huge and you're keeping them as pets rather than part of the clean-up crew - for the most part, they'll find their own food on the rock. I usually drop in some food for my hermits once a week or so just to make sure no one's going hungry, but the rest of the time I leave them to do their job and clean up algae, poop, or leftovers.
One more thought... if you're thinking of investing in an easier to read hydrometer, my advice would be to spend a few extra bucks and get a refractometer. They're very easy to use/read, and much more accurate.
 
AquariaCentral.com