Pond Boss Forums AERATION Systems questions Aeration: 24/7 or 12 on 12 off

OK, guys, I've read through many, many threads on aeration, learned a lot, decided it was something I wanted to do for my new one acre pond, spec'd the system with a reputable manufacturer and installed it at approximately 22' depth this weekend. Ran it for the recommended 15 minutes today (it ran like a champ) and will continue for the 8 day startup period. Now the Question:
Can I get basically the same aerobic benefits for my fish and my pond's aquatic life by running evening hours 7 p.m. to 7 a.m. rather than running it 24/7. This tough economy and the cost of energy leads me to ask questions I might not have asked a few years back...in other words I don't want to spend money unneccessarily.

My goals are basically: protect my fish from seasonal turnover and low DO levels (and hopefully increase my pond's carrying capacity); lower the possibility of unwanted algae; keep bottom muck from building up too much (the pond is surrounded by woods).

I'd appreciate your thoughts.

I've had several lookers but no reponse to my post...I know there are some of you out there who have experience with testing 24/7 aeration vs. 12 hrs on 12 hrs off. I'd sure appreciate the benefit of your experience...

git1fiddle,
I have been running my system 24/7 spring to fall, but am now in the process of building a controller that will run it based on the temps in my water column. You are right, power usage is a killer. My 3/4hp pump runs about $90/month. There isn't much left to cut out of the budget. This past fall I first tested for Dissolved Oxygen with the pumps running, and since then with them off. There was no appreciable difference, (but that was late fall). The reason I haven't run it on a timer is that my four aerators are at 17', 9', 6' and 5' and it is difficult to get them all started and balanced on one pump. Once they are going they are just fine. Hopefully I can get my programming to work and save some $$ this year. Suspect with the 7pm-7am you are hoping for time-of-use on the meter. I may end up going that way too. Hopefully someone else has cycled their system and can give you some more info.

Thanks for the input, Jeff. Man, that water temp controller sounds interesting, but way past my technical skill. My 7 p.m. to 7 a.m. proposed schedule comes more from my reading that DO levels tend to drop when the sun goes down, and reaches its lowest point just before sunrise...but now that you mention it, that time frame would keep me away from costly "peak" killowatt hours.

I still drive a pickup but I'm keeping it at 60 mph which improves my gas mileage by nearly 15% over my usual 70 mph...though it does get me some looks and a few horn honkings.

When I run the aerator, it's only a 1/4 hp motor, so the electric bill doesn't change much. I believe that starting and stopping a compressor adds to the wear and tear more than running it continually. Nothing factual to back it up tho.. I tried running the aerator only when ambient temps got below 70°F in hopes to allow trout to over summer in the pond, but the surface water would heat up during the day, and mixing it, even with cool nighttime air did in the trout. When I run the aerator, I run it 24/7.

A pond surrounded by woods and its organic inputs creates a significantly higher biochemical oxygen demand thus requiring more water movement (oxygenation). Also regularly feeding fish or fertilizing are very important factors that contribute to longer aerator run times. I assume the system was probably designed with the intent for it to run 24/7 to create the proper turnover rate? Implementing 'over kill' in designing an aerator provides a greater opportunity for reducing aerator daily run time. Depending on the system specs and the amount of organic inputs are the two main items that will contribute to if the system can operate less than 24 hrs/day. There are also other important factors to consider. Do you have a way to measure bottom water temperatures in the pond's deepest area where I assume you have one of the diffusers?.

Bill...
The diffuser (a single cluster of four 9" diffusers) sits at 22', almost in the center of my generally rectangular pond which is just shy of 1 acre. The system's capacity is 7800 gpm, so if I'm figuring right, if I average a 12 foot depth, the system should turn the pond over approximately every 8 hours.

I have not measured the bottom water temps at 22 feet, though I suspect I could find a weighted thermometer at Bass Pro and drop it down with a fishing bouy. What temps would I be looking for and how would I use the temp info in determining running times?

As far as organic material, my watershed is hardwood (oak/hickory) and no runoff from cattle or farming operations. We have cleared the shoreline of large trees, but there are leaves in the fall. Water is a nice green/brown with good visibility, and the startup on the aeration system has not caused any noticable increased sediment.

Hope this info will give you the input you need to help me figure out efficient but economical run times...thanks

Bill...
I forgot to mention that I am not feeding my fish....bluegill / redear /stocked last fall and will stock LMB in May...also have not fertilized. Pond was limed when dug last summer.

This topic will be explained this weekend on Saturday morning at the Pond Boss Conferernce IV at Big Cedar Lodge, Branson, MO. Topic of "Do Ponds Really Need 24 hr Aeration" by Bob Lusk. You should try to attend. There will be lots of VERY good information on many topics for new pondowners.

Not feeding the fish nor fertilizing will help in allowing for shorter aeration run times than 24/7. A new pond also helps. As the pond ages expect to run aerator longer each day especially in mid summer or whenever the water is above 80F at the surface because the dissolved oxygen requirements of the entire pond (oxygen budget)increase as the pond ages and accumulates more nutrients, plants and organics. Also as water warms it cannot hold or absorb as much oxygen. In warmer water the DO is lost or consumed faster, thus it useds more DO per day. There are numerous "it all depends" with each pond and aerator run times.

Ideally to answer your question one should measure dissolved oxygen (DO) at the bottom of the pond. The goal IMO of every aeration system is to maintain DO ABOVE a bare minimum of 1mg/L or 1ppm. Higher DO than 1.0 is MUCH BETTER. For good fish life DO should be a minimum of 3-4ppm. But IMO one's goal should be to maintain enough DO to keep aerobic bacteria and invertebrates alive in the bottom surface sediments. DO meters are expensive - $350-$800. Often (at least in northern areas) one can 'measure' the amount of mixing at the pond bottom by monitoring the bottom water temperature and comparing it to the surface temperature. Get yourself an electronic digital thermometer with small probe with cable. These are most commonly available with ten ft cables. I think two cables can be spliced and water proofed with silicone sealer. Once cables are spliced, calibrate the unit with a standard thermometer. Check one bay for fishing temperature meters, some will longer cables of 20ft or more.

Now for the unknown. The following method is not without risk. In my experience with bottom aeration, if the bottom water is kept within 3-4F deg. of the surface water, one can assume adequate mixing with at least some DO on the bottom. Run aerator enough daily to achieve this temperature similarity between top and bottom. Well mixdponds will have only 1F difference between top and bottom temps. NOTE this probably will not be true for fertilized or eutrophic ponds. Other experts, especialy in areas south of Ohio should verify this concept. Also to be safe and do NOT believe this blindly, you should have your DO actually measured in mid-summer while using this philosophy or technique by someone with a DO meter.

I agree with all of the posters here including Bill who is obviously extremely knowledgeable on the subject. I don't crank up my summer compressors until the time the ponds start to stratify in late May and shut them down when the water turns over. I hook up smaller compressors and a single stone in the winter in 3 to 4 feet of water in the ponds I have fish in.

Readers of this topic stay tuned until after the forum when I will hopefully remember to report back my notes of what the 'Fish Master' Bob Lusk has to say about the topic.

Thanks, Bill, I'll look forward to your post. BTW, the venue for the forum, Big Cedar Lodge is a fantastic place if you haven't been...