We have a customer that is using a single Gast 0523 rotary vane compressor (1/4 hp) to push air to 3 different ponds at the same time. 5 single membrane diffusers. That single compressor replaced two Koenders 1/4 hp compressors (that could only run 3 single membrane diffusers), and the Gast is pushing more than 2x the air volume of the two Koenders for half the energy cost.
BUT the Gast rotary vane isn't the one I'd recommend for a deep pond, that would be a Thomas Rocking Piston compressor. They can operate to a higher PSI than a Gast rotary vane.
Both the Gast and Thomas are easily rebuilt when needed.
: ) the OP is looking for a pump for his single .2 acre pond.
Which one would you recommend to him? The often here recommended '5 pond' Gast?
For the OP, for the longest pump life, I would look at getting a pump (paired with 2 Vertex XL1 air stations, one for deep water, one @ 3' water depth to keep part of the pond open in the winter) that produced 4 cfm @ 6-8 psi. That way the OP isn't running the pump at or near max rated psi and shortening the life of the pump. Just like anything mechanical, the harder the item is worked, the shorter the life of it is.
Combining that cfm/psi with those diffusers will allow the OP to run the pump 8 hours per 24 hour period and move enough water to properly aerate his (or her) pond. They should turn the system on so the system is still running for 1/2 hour after sunrise.
Using different diffusers changes the equation, and are unknown, unless the diffuser mfg lists the lift rates @ different water depths in GPM.
The shallow water diffuser doesn't have to be the Vertex XL1, in fact a diffuser that produces coarse bubbles will work better at keeping a hole open in the ice. BUT unless the OP is handy or willing to make their own diffuser base, (it's easy to do) I stand by my recommendation.
