Pond Boss Forums AERATION Should I aerate? Know the depth and diameter of aerator "plume"?

Hi. I have a 1/2 HP Kasco 2400A surface aerator centered in my half-acre triangular pond. Where it is centered, depth is about 15 ft. Deepest part of the pond is 18 ft. My question: Can anyone give me the circulation "plume" diameter and depth expected for underneath my aerator? I am hoping that someone in the aerator industry has an answer that is demonstrated by actual product testing rather than a guesstimate. The answer may shape my decision on investing in a bottom aerator instead of continuing to use my already-purchased $900 surface aerator.

SW Ohio - That's a great question with a somewhat complicated answer. Kasco surface aerators are very effective at delivering high volumes of oxygen (O2) into the upper portions of the pond, up to 3 lbs O2 per hour. This oxygen will spread throughout the pond and provide plentiful amounts of O2 in the upper portioin of your pond. So as a surface aerator, it does a bang up job. As you've probably seen in your pond, the surface agitation and ripple effect is pretty extreme and will (should) radiate across most of the pond's surface.

Being a surface aerator, it pulls water from directly below and around it up to a depth of maybe 4-6 feet. The maybe portion is impacted by time of year and/or the stratification in the pond. Middle of summer, hot temps with little breeze, that pond will be heavily stratified and the aerator will not be impacting the layering all that much. Reason being is that the density of the bottom water is much heavier than the less dense surface water, making the surface water easier to move/circulate. There may be some local disturbance of the layering right where the aerator is, but it will not be impacting the surrounding stratified area, especially in a pond that has a max depth of 18 feet.

Plume is generally used to describe the rising cone of bubbles up from the bottom typical of bottom diffused aeration. What you have currently is where the flat part of the cone starts at the top and stops about 4-6 feet down, where bottom aeation starts with the tip at the bottom and spreads out as it rises to the surface. So "plume" may not be the best way to describe it, more like a "cone of depression". So maybe your "cone" starts with a 10-15 foot radius (30 foot diameter) and tapers to a 5-10 foot diameter point underneath the aerator? It's possible that it is more cylindircal than cone shaped, but the area of impact (in terms of direct measureable ciculation)is limited to a localized area. For a surface aerator that's pretty good. If it were being used as a circulator, prop sideways instead of vertical, it would move more water, but oxygenate less.

These are not solid, tested numbers, more like an estimate based off in the field experience and observation. I'm sure one of the Kasco people could jump into the conversation and provide you with a much more detailed answer than what I have here. Hope this helps.

Clarke DeWitt
Aquatic Eco-Systems

Thanks, Haplo. The "cone" image helps me to understand the aerator's effect. I haven't done any temp or DO testing in a widening area from the Kasco, but since installing that surface aerator, it seemed like the cold layer 25 feet to the left of the aerator, which is where we do most of our swimming, was almost non-existent (at least 10 feet down). So for increasing DO and mixing, my surface aerator is doing a pretty good job (unless I turn it off for 4 days and essentially cause a fishkill...see my earlier posts in August). The dual bottom bubbler that I am considering, since the pond is triangular, will likely do a better job at total destratification, and start to reduce the muck. I am restocking the pond after a near total fishkill last August, and want to get through summer 2012 without hauling any dead fish up into the woods. Last question, do you see any need to run the surface aerator in addition to two bubblers?