I got a couple of air pumps from Champion Lighting and supply for my 3000 gallon pools. They push a lot of air and are very reliable. I have had them going outdoors for 8 months now and no problems. They are set up for ponds, so head pressure is never a problem. I got the supreme air pump ap 100, but for your application I would try something like the 20 or 40. If you might expand later go bigger and put in a splitter to divert it so your fish aren't in a whirlpool.

www.championlighting.com