Cecil:
Thanks for all the feedback- helpful info. I think we will be measuring both temp and DO alot more this spring and summer. WE painfully learned 3 years ago that we fried the rainbows in late June early July by continuing to run the fairly powerful 1/3 hp dual diffuser system right at the bottom of the pond (at about 8 ft. depth) thereby creating a "convection oven" which raised temps to 72 degrees and our rainbows starting jumping out, swimming like sharks - all the telltale low DO and temp shock symptoms. Of course by the time I turned it off, guessing what was happening, it was too late. That won't happen again!
I had a bet with my 12 yr. old to guess the temp last week, when we were at our West Branch 1/3 acre pond and I guessed 43 and he guessed 39,the darn bottom of the pond (12-14 ft. depth was exactly at 39 degrees!
After some learning int he past 6 months, our plan is to re- install the aeration diffusers on teh shallow side (ot excavated recently) at about 5 ft. depth) and away from the severe drop off. and then possibly aerate during the fall / winter / spring and only at night when temps drop in the summer (we're working on obtaining a combo timer / temp switch).
Questions- Is this a reasonably good strategy for aeration??? And, are there any low cost, timer, temp actuator electrical switches made for this purpose???
Also- it make alot of sense that we need more in-flow to keep the temps cooler. At a calucation of 15 gpm (or 21,600 gallons per day) into a 900,000 gallon pond, it takes 41 days for the water to completely turnover (seems too long doesn't it? Outflow by the way is via a 5 inch pipe built into the pond in the 1950's that is about one ft. from the top (we put an extender for max. depth)and runs about 3ft. away into a cattail wetlands area.
