Pond Boss Forums AERATION Should I aerate? Partial aeration?

Given my recent fish kill I'm seriously considering some sort of aeration solution. This is the third time I've considered this since I built the pond. My real issue is that given the size it's not cost effective to aerate the entire BOW. And based on what I've read here and on other sites it appears that partial aeration is a controversial topic, with some experts indicating it can do more harm than good.

Here's the facts on the BOW in question.

Irregular shaped, 7+ acre BOW. Average depth 14+ feet, deepest point almost 30 feet at full pool. Issues with weed control due to phosphorous and nitrogen runoff from neighboring ag fields.

Goal for the BOW is 'balance' if there is such a thing.

Current fish are LMB, BG, RES, BCP, CC and until the last week or so HSB. I'd surmise that most if not all of the HSB were killed due to a large influx of water from the recent deluge - probable cause of mortality is rapid turnover of the pond due to major temperature change from the rainwater. Other possible causes and/or contributing factors could also be rapid die off of vegetation, again due to rapid temp change.

It would be cost prohibitive to completely aerate, so the question at hand is, would this situation have occurred (or something worse occurred prior to this) if partial aeration was in place, likely in the deep water areas near the levee?

Dale, you know your bottom profile better than any of us. There's 325,851 gallons of water in one acre foot. Can you give us a rough estimate of how many gallons of water are in the pond?

The bottom contour of the pond will dictate how many gallons are in it, but with you knowing the bottom contour, that might allow you to figure out the volume of water in the pond better than us guessing. i.e a guess would be you have an average depth of 15'. So, 7 acres x 15' water depth x x 325,851 per ac/ft = 34,214,355 gallons

Typically you want to turn over the volume of water in a pond a minimum of once per day. You can go slightly under that but the rule of thumb is minimim 1x as a bare minimum.

A single XL5 in 30' of water will move 21,312,000 gallons per day, and needs a minimum of 2.5 cfm at that depth to do that. An XL4 diffuser will move 15,552,000 gallons per day when placed at that depth and will need a minimum of 2.0 cfm to do that. So, theoretically a compressor that has an output of 5.0 cfm at 16 psi would work as a bare minimum.

The calculations are more complex than that due to the surface area and area influenced by each diffuser, but that gives you a figure to work with for starters, and a rough idea of system requirements. That can be fine tuned with your knowledge of the pond bottom and the resulting total water volume.

Dale,

Every pond or lake is different, and there is often more than one contributing factor, and from the sounds of it you might have a few things working against you. Have all your fish kills been after a major storm? Or are there any common conditions between your fish kills?

If the phosphorous runoff is excessive you may be fighting a very difficult battle. You may be having huge swings in oxygen demand. Is there any way to limit the runoff from the fields?

The only real way to know what is going on is it get yourself a DO meter and start monitoring your water. It sounds like you have O2 issues, but getting to the root of them is going to be critical. The DO readings should help fill out the picture and let you know for sure what is happening and when.

Regarding aeration, it would be helpful if you could provide an image from Google maps so we could see just how irregular it is. You have some very nice depth at 30 feet, and a good bottom diffuser at that depth will move a lot of water.

I am a firm believer in some aeration is better than none. You have a refuge or place the fish that are looking for more air a place to go. Nature is not stupid.

If your into turning your pond over for more fish capacity then I would expect you need to do the whole pond.

A refuge is better than trying to save the pond with rotary mower stuffed half in the pond adding air to it or another creative way to agitate the water.

Cheers Don.

Dono - I'm more interested in a refuge...not terribly concerned about more carrying capacity. It's pretty much only me and my family that fish it so with just 'wild' capacity it's got WAY more fish than we can catch.

Littlebass - in the 5+ years since I built the pond this is the only kill I've ever had. It appears that the total damage is:

3 CC's (10-15 lbs each)
17 HSB's
6 BG's
1 LMB

Almost every single floater was down at one end. And that end was NOT the drift end, so my assumption is it was some sort of relatively localized kill in the 'shallow' end. The area where the floaters are is the only real shallow section of the pond.

No there really isn't any way to divert the runoff, at least not without major cost.

As a pond ages fish kills become more likely due to the effects of eutrophication which consumes dissolved oxygen. As eutrophication increases the biochemical oxygen demand (BOD)increases which often leads to DO shortages.

I am going to agree with Don on this one. In this case I think some aeration is better than no aeration. You are the best judge of your situation, and if a large influx of water caused a turnover leading to a fish kill, that almost surely means you have anoxic conditions in the lower waters of your pond.

When these lakes and ponds stratify in the summer months it takes an enormous amount of energy to get them to turn over, and that rain could very well do just that. In larger BOW the wind will will keep the BOW mixed, but in most cases in the smaller lakes and ponds there just isn't enough surface area for the wind to be effective and that is where aeration comes in.

You have some very nice depth, so bottom aeration should be effective. Just remember to start up the system slow.. run for 15 minutes the first day, 30 minutes the second day, an hour the next and so on until you are running 24/7.

Slow aeration start up is only necessary when the pond is stratified. Starting early in the spring when water is around 50F and little if any stratification,, aeration can begin 24/7 if desired because there is not anoxic zone to be brought to the surface good water zone.

DL I would do this for sure! At least you would have that acre or 2 safe zone in your deeper water where it counts the most! The shallow water (under 6 feet) should take care of itself for the most part. Will be interesting to see if you have any more issues if you do put a system in. I bet you won't. Unless something really crazy happens.

RC