One last item Cecil, you mention "boil" and that is a good term. One of my displays is a 1.6 CFM piston pump that is manifolded to each a 7 inch round airstone a Great Lakes 4 stone ALA4 GL and a rubber Membrane Coactive airstation.All have the same hose length and are in 12 ft of water. A lot of visitors here tell me that their diffuser boils the water. I tell them that the round stone is turning 500-600 GPM and switch to the Great lakes @ 1250 GPM and lastly the Co Active which is turning 2778 GPM and can you tell me which is which.This set up is 50-60 ft off shore and the boil "looks" the same on each one.(no one has got it right yet) My point to this display is that a boil is often a real fooler on knowing if your turnover is what you want and need it to be.I test many ponds with a good boiling diffuser but with low DO and 9 times out of 10 the diffuser is the problem not the pump. In your case with small impoundments your odds are greater that you are getting a good turnover as you can confirm with your DO meter.Aerate properly and forget the DO meter for the average pond owner and $600.00 saved, Cecil your ponds are not average however. Ted
