It certainly looks like you have done your homework! I don't know a thing about solar systems, so keep that in mine when I say...I can't add much to it from my experiences other than...

1.) Go with the largest hose you can afford. This will reduce wear on the pump, increase air flow/water movement, reduce pump noise (at least with the 0523 - the lower the back pressure - the lower the noise), and allow for longer runs of hose. There is a substantial difference between 3/8 and 5/8" hose with regards to pressure losses in the lengths you are running.

2.) I am finding that the 0523 is much more pump than my 1/4 acre pond needs (probably a bit large for your 0.4 acre pond too) and I, certainly, could have gone with a diaphragm pump. I can't say that I regret the decision, but I have been running my 0523 only 5 hours a night yielding about 1-1/2 turnovers in that period. The summer here requires nighttime running and the noise during the night is certainly not an issue for me. I have also brought my diffusers up from the 8-9' depths to a more shallow 6' depth to reduce turbidity (I don't think it's helping...crawdads are my scapegoat at this time)...It still does not develop a thermocline in this configuration...less depth means less pressure requirements, less energy usage, and more air flow. It does reduce the water movement a bit which requires more run time.

3.) As we all know, all ponds are different...Mine is triangular and small. My pond more closely resembles a bowl than a larger kidney shaped pond, so I would suggest going with a slightly large pump than you think you need in case a third diffuser is desired at a later date. Flexibility is nice to have for getting past the learning cure period. A pump that is slightly over-sized can be run less to do the job (same energy consumption, but with more short term demand, right?) where as a pump that is too small is yields a dead end.

4.) As far as energy costs are concerned, forgive my lack of experience here...A higher wattage requirement on a pump that can be run for lees time may be as cost efficient as a lower wattage pump that has to be run longer. So long as your solar system can supply the on demand power for a particular pump, a shorter run time can balance out the comparisons...right? I think what I am saying is kilowatt-hours need to be calculated and considered. In terms of WORK, if your goal is for 2 turnovers a day...it's pretty much the same amount of work being performed just in different time spans...work in equals work out.

I don't know if my ramblings have helped you out much as you have selected 3 pumps that are all very good for the job, but here's my opinions...

The Hakko does not leave any room for expansion if needed, but will be the most quiet. Could you add another down the road without kicking yourself?

The Matala and Gast have plenty of room for a third diffuser (maybe a forth), but will be louder.

My little pump house (small outhouse) is made of metal with barn wood siding and sits about 60 feet from my dock. I can hear it at the dock, but it does not hinder conversations at all, but if you are the type that wants pure serenity at the pond...the 0523 is not for you. It will be humming along letting you know it's there. Keep in mind that we run these systems at night MOST of the time. The pump was running this calm morning and I really had to listen for it while on the front porch, approximately 170 feet away.

Sorry to go on and on, but I have chores to do this is certainly more fun...thanks for the sidetrack!

Last edited by Quarter Acre; 08/31/19 09:32 AM.
Fish on!,
Noel