Thanks for the replies! I cleaned all the aquarium tanks up again, and I've been wiping the outside on the tanks where I've seen the bugs with rubbing alcohol - evaporates quick and seems to kill the mites, so it seems to work pretty nicely. The amount of the mites (or whatever they are) has drastically decreased - I'm guessing the last batch of corn cob bedding I put in had harbored them, and the gerbils covering their water bottles in bedding (i.e. causing the water to leak out) probably made it a great breeding ground for them. I've only seen a few mites on any of the tanks today, so I'm hopeful that with diligent cleaning I'll be able to get the infestation wiped out.
I haven't seen any of the mites on the gerbils themselves, and all the cages have 2-3 gerbils so I figured at least some of them would have been exhibiting odd behaviour (itching, excessive groomimg, acting apathetic, etc) if they were getting bitten. The odd thing is that the bugs seemed to be congregating on the top of the tank (black metal cage top), very few of them were IN the tanks except for the top of one water bottle - which is all the way up at the lid anyway.
I read a post somewhere that was suggesting that the tiny bugs appearing on cages might be some kind of scavengers going after the waste in there (buried food, fecal pellets, etc), especially if they get the tank moist. I don't remember there being any recommendations to get rid of them, but now that I'm at home I can't find the post anywhere through Google.
Also, I have seen a good amount of posts complaining about bugs coming from corn cob bedding, so I really think the bedding combined with moisture was the source. I guess I should get a freezer trunk just to freeze the 40lbs bags of it before using it.
If the infestation does comes back, I'll take in at least a few of them to get checked out and ask the to give me a perscription for medication for all of the gerbils. Since there's 10 gerbils (I learned that the pet store employees had no idea what they were talking about when they sold me only 'males'), and the recommended exotics' vet here charges $89 per animal, I'd rather avoid that $900+ dollar trip if I can. I checked the link posted above and saw some other posts about mites, but they all look bigger and darker in color - these bugs are really tiny and light colored, so they don't fit the typical mite or flea descriptions.
I did find recommendations for diatomaecous earth on a variety of pages. Sounds like the food-grade stuff is safe to pets and people, but kills insects - I might pick up a bag of that and have the gerbils take their sandbaths it for a few weeks. Anyone used it around their pets to any good results?