Ryan :

Can't answer them all but here is some info on heaters.

As noted it is a cost issue. See the link below for a temp. controller for a heater at about $100. The link in post above has quite a few options including pond heaters which may work well for a small RAS but most inexpensive heaters are usualy set for a bottom temp. of 40 and only adjustable above that temp. ewest

http://www.aquaticeco.com/index.cfm/fuseaction/product.detail/iid/9207/cid/2214

pond heaters:

http://www.aquaticeco.com/index.cfm/fuseaction/listings.categories/ssid/378