If you're talking about George's set-up, you can purchase the point four micro pore diffuser from any good aquaculture supply company. The O2 tank, & flow valve - hit your local welding supply store. You might also give Greg a shout.

The cooler recirc system is found in Bass Pro, or buy the pump (Bass Pro, Cabela's, maybe Wally World) and DIY from parts sourced at your local hardware store.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
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3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).