For a good start try a tractor supply store for plastic water troughs. I got my 6' round for $160 I think. Cheap and easy. Other than that building one from wood is also a plan. I'm starting my 12x6x3 pond build thursday
Mine will be going into a 8' intex pool (nearly 700g) with a wet-dry filter and I'll probably have to use more than one heater to heat the entire thing. Be prepared for a considerably higher electic bill.
There are tons of DIY filters for large tanks & ponds on the forums
im a member of oscarfishlovers and wow i kinda got a negative reaction on getting this guy, one guy, a leader of the site recomended i take it back, thanks guys for being possitive on the subject, i think i have found a new home site
U will like it here but be careful it can be addictive. When I left sf and back to civie life I had a 100gal......now I'm building a 1500 to house my monsters...all because of this site. Lol