I thought I would post my experience with starting up my aeration system this summer so that others would have something to compare their start-up to.
A little background, My pond is 1/4 acre, 10 foot at the deepest, with an average depth of about 6 to 7 foot (very steep sides). I use a Gast 0523 and 3 vertex diffusers. The deepest diffuser is out towards the middle, but only set at the 7 foot depth while the other two are much closer to the bank set in the 4 to 5 foot depths. The deepest diffuser receives most of the air flow while the others are dialed down to about 1/4 of the flow. I feed this April's 2 to 6 inch stockers daily about 1/2 pound in the evening and aerate from 9pm to 9am.
Time for the data. Temp records before, during and after aeration start-up...
Started taking temp readings (Degress F) on 5/2/18 (without aetartion)...
5/2 - 18" down from surface = 75, 7 foot down = 50, secchi = 24",Outside Hi/Lo=87/65.
A steady rise in temps and a quick increase in visibility brought me to 6/4/18 (still no aeration)...
6/4 - 18"down=80, 7'down=68, secchi=36",Outside Hi/Lo=93/75.
Aeration began on 6/24/18 and I had started taking an additional temp at the top 4 inches near the surface. I did the prescribed start-up of 15 minutes first day, doubled for the second day and so on, EXCEPT I moved a diffuser deeper (from 5 to the final 7 foot depth) and stepped back from 6 hours run-time to 2 hours and started the doubling process again to avoid any heavy turbidity change...
Temps before aeration start-up (all temps taken around 5:30pm)...
6/14 - Surf=90, 18"down=86, 7'down=70, secchi=31", Hi/Lo=94/68.
6/17 - Surf=94, 18"down=88, 7'down=72, secchi=24", Hi/Lo=95/75.
Days Following start-up...
6/24 - Surf=82, 18"down=80, 7'down=72, secchi=24", Hi/Lo=89/68.
6/25 - Surf=82, 18"down=79, 7'down=72, secchi=20", Hi/Lo=91/62.
6/26 - Surf=76, 18"down=76, 7'down=72, secchi=22", Hi/Lo=79/66. NOTE: 2-3/4" Rain before readings.
6/28 - Surf=94, 18"down=84, 7'down=72, secchi=24", Hi/Lo=85/66.
6/29 - Surf=94, 18"down=84, 7'down=72, secchi=20", Hi/Lo=78/66.
7/1 - Surf=88, 18"down=86, 7'down=76, secchi=18", Hi/Lo=87/72.
7/2 - Surf=90, 18"down=86, 7'down=78, secchi=22", Hi/Lo=88/69.
7/3 - Surf=92, 18"down=86, 7'down=80, secchi=24", Hi/Lo=94/73.
7/5 - Surf=92, 18"down=86, 7'down=80, secchi=24", Hi/Lo=95/74.
7/7 - Surf=89, 18"down=86, 7'down=82, secchi=18", Hi/Lo=90/65.
Running aeration about 12 hours a night (9pm to 9am) at this point. and I missed a week due to work. I also started taking a temp reading at the very bottom ( about 10 foot deep)...
7/17-Surf=86,18"down=86,7'down=84,10'down=82,secchi=16", Hi/Lo=95/75.
7/19-Surf=82,18"down=82,7'down=80,10'down=80,secchi=16", Hi/Lo=80/73.
7/21-Surf=86,18"down=84,7'down=78,10'down=78,secchi=20", Hi/Lo=88/68.
7/25-Surf=86,18"down=82,7'down=78,10'down=78,secchi=20", Hi/Lo=91/62.
7/27-Surf=84,18"down=80,7'down=76,10'down=76,secchi=20", Hi/Lo=84/62.
7/29-Surf=78,18"down=76,7'down=76,10'down=76,secchi=18", Hi/Lo=78/66.
My take-aways...
Looking at the days before aeration started (6/14 and 17) the pond had a 20 to 22 degree difference between the top surface and the 7' temp and a secchi clarity of 24" plus. This 20 degree temp difference and clarity drops to 10 degrees and under 24 inches immediately. Too fast in my opinion, but that's what the data tells me. My calculations suggest that the three diffusers, at 12 hours a day, should turn my pond over 4 times per day. This reduces to a 0.08 turnover in only 15 minutes (that's about 1/10th of a turnover the very first night). Maybe this little bit of a turnover is enough to make a big difference at the surface. Comments?
Now that the system has run for an extended period of time, the temp difference between the bottom and the surf tend to be 10 degrees rather than the original 20.
SideNote: If you look at the surface temps, they dance up and down pretty radically where as the 18" down temps and below tend to change less abruptly. Using surface temps to evaluate the pond could be risky. I suggest looking at temps at the 18" below surface for any important evaluations.
Even though the summer has gotten hotter, the surface temps are staying down below 90 and the 18' down and 7' down numbers remain consistent and in a decent range. Even though the temps are higher than I would like, I think the pond is in much better condition with the aeration and at less risk of a fish kill.
The clarity got worse after the diffusers were activated, or maybe better if you look at it right. Just before adding air, I had a small FA outbreak. Shortly after adding air, the FA disappeared (I raked alot of it out). Maybe the reduction in clarity due to sediments being added up into the water column also reduced the production of FA. Sounds like natural dye to me, what do you think?
The morning clarity is obviously less than that of the evening. You can see "dirty" water veins of the morning and a protein film with bubbles that must be caused by the aerators. Then in the evenings, these veins are gone and the surface is typically very reflective and clean looking.
One thing that would have really added to this post would be DO2 readings, but I do not have an O2 monitor.
I'm going to stop here, my mindis going numb. I will try to chart some of these temps another day and see if there are any trends to speak about.
