Pond Boss Forums AERATION Systems questions How to suspend diffusers at half height.

I'm sure there is something obvious I am missing. I'm thinking about getting my 7' pond dug out deeper - 15 to 18 feet so that I can sustain trout over the winter and summer.

I've been told that a diffuser is a bad idea as it will de stratify cold water at the bottom which trout need and I should have gotten a fountain but I saw a recommendation somewhere that diffuser can be suspended at half height in the summer.

How does one do this? Won't it just sink. Should I attach a mooring rope to the other end of it opp side from the airline and attach it to the bank. Then pull in the rope in the summer. Perhaps a mooring rope on both ends to prevent damage to the airline ?

Do NOT worry about warming the water temps by installing an aeration system. If your pond will be 15ft deep, the temps below the 6ft depth will still be in the sub 60 degree F which will sustain your trout population.

If the pond is not aerated properly, bottom up, your oxygenated water will be on the top layer causing the trout to stay in the shallower water where temps will be higher and can cause a kill off.

If you're shopping for a quality system, contact Sue at Vertex. They are the best on the market and actually have factual numbers when it comes to water turnover and what their systems can and will do.

Ummm....... In my 18' deep, 1 ac pond, with a bottom diffusion system, set to run at night, only when ambient temps were below 70°F, destratified my pond in less than 2 weeks and my RBT died. Temps top to bottom were in the mid 70's.

I had RBT live almost 4 weeks longer by not aerating at all the next year. Surface water temps were in the low 80's.

I had a client that kept RBT alive until the end of July in his 7' deep pond by using a combination of bottom diffusion systems AND a Kasco surface agitator. O2 levers were at saturation down to the pond bottom. RBT were still alive in 76°F water due to the high O2 levels. That's roughly 5-6 more degrees than thought possible.

Another plug for Sue here too.

In our pond I thought the same thing deep = cold. We are at 16 feet on one end and 14 feet on the other end. Both ends have bottom defusers set at about 18"s off the bottom. The whole pond warmed to 70 having them run 24/7 in the summer. I would have never believed this unless I seen it that two vertex disks could move one acre of water that deep to warm it all that deep too.

I just have perch and no trout but to help cool the pond I run my waterfall at night and not during the day when the water temp rises.

Cheers Don.

If the diffuser keeps D.O. levels good at the half way point by suspending them it won't help if the deeper water goes anoxic even if the water is cold.

Pondpro,
To further my understanding, can you explain your comment below against the experience of others in the posts below yours? Perhaps this is a situation that requires some explanation of the 'it depends' part of the equation?

I'm curious because up to this point in time, I thought I could cool my pond by running my aerators at night and get the cool water from the air temps to 'flip' back under to the bottom. But now it sounds like real life experience from other pond owners suggest you will only warm and destratify the whole pond to 70 degrees by running the aerators at night.

Makes me wonder how to keep the bottom cool? I do have the option of pumping 53 degree well water to a pipe that comes out on the pond bottom, but I imagine again with my diffuser running that mixes through pretty quickly. I can only run the pump a few hours during the overnight as the pump is needed at full capacity to run my sprinklers and my house water needs during the day. I can't imagine I can pump enough water in my 1/3 acre pond to totally exchange the water or even to bring the level up.

Pond Pro said:
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Do NOT worry about warming the water temps by installing an aeration system. If your pond will be 15ft deep, the temps below the 6ft depth will still be in the sub 60 degree F which will sustain your trout population.

CanyonCreek,

I run a diffuser at night in my trout pond and even at night on the hottest days of the summers (highs in the 90's) and most of my water column from top to bottom except for the top few inches stays right at about 60 F.

However this pond is small at only 1/10th acre 59 X 88 feet with steep sides, and I run in 51.6 F. degree well water at 45 gpm 24/7 in the summer.

Thanks Cecil,

So what is the difference where the 2 posts above had even water temps from top to bottom and you are able to keep your water at 60 even with diffuser? Your pond is smaller so the diffuser should have an even easier time of mixing the entire water mixture to equilibrium? It must be you replace cold water fast enough to keep it cool.

I'm experimenting with running mine 2 different ways. The last few weeks I'm running it say 30% capacity using a valve that I adjust with a crank that twists in and out. If I 'choke' it down, I can save water pressure for other needs, and can run 24/7. Downside is it creates turbulence or noise in the valve area in the house and it sounds annoying with all the gurgling from my basement. My brother who does pump performance curves all day tells me today that it is far better to run the pump wide open with the valves all open so that the pump can get higher up on the performance curve and really push the water. He figures even if I can only do that for 4 or 5 hours at night I might pump more water and less work on pump.

Make sense. Maybe the trick then is to run the aerator at night, and add lots of cold water. I don't need RBT range cold water but I thought keeping it a bit under ambient summer air temps might make the fish more comfy.

I have wondered about running a heat exchanger loop like a heat pump would have to cool a small pond. Taking in the warm top water and pumping it into the loop and then just back into the pond. If the loop is long enough and in the 53* ground you could keep the water temp year round.

One would have to calculate the thermal loss of the surface area of the pond. It would be like creating your own cold water spring.

Cheers Don.

Bingo!

The pond has a volume of about 100,000 gallons and if I remember right 45 gpm is 64,800 gallons of water every 24 hrs.

The downside is you would not be dilluting mebabolic waste products and flushing them out as you do with the infusion of freshwater with flow through. Trout are very sensitive to ammonia and nitrites and even nitrates, which could become an issue at some point depending on the density of the trout.

It is unlikely that the conclusion I should draw out of this is that to have a successful trout pond, I MUST have new cold water going into the pond to ~ cycle out the old water in the pond daily.

At least one very knowledgeable trout farmer here runs ONLY fountains/surface aerators and does not recommend diffused aeration; now I'm not suggesting I agree or disagree with this recommendation but he does successfully raise a large quantity of trout and isn't destratifying the water column and his trout aren't dying because of lack of oxygen in the summer in the cold bottom layers.

I'm guessing there is some appropriate answer between the extremes that will result in a deep pond maintaining cold water at the bottom that trout will survive in.

canyoncreek,

My recommendation and $.02 is coming from my experience in the field, managing almost 1,000 ponds annually, many of them that have RBT in them... in Michigan. We do some pretty extensive testing on aerators, mainly Vertex, how they operate in the field.

Although the other's input may sound logical, there is one thing that they indicate which may not be taken into consideration.. and that is when they run their systems and how they run their systems. (And as for trout farms... their ponds are typically less than 10ft deep with continual water changeover and high volume surface aerators to sustain DO levels... so they have high DO and cold water)

Running a system only at certain times of the day could actually be causing more harm than good and cause some of the problems that some have written about. When ambient temps & water temps increase, DO decreases.. especially when an aerator is NOT running. So after a warmer or hot day where there could be a dip in the DO levels at the top layer of water and little to no DO at the bottom of your pond due to NOT running the aerator, your fish will be caught in the mixing process when an aerator is turned on.. Colder, DO lacking water being pushed to the top layer and forcing the already DO decreased warmer water to the bottom... Essentially, in my opinion, fish loss due to the operation cycle of the aerator, not the aerator.

I'm only giving you my input that is based off of my professional experience in the field for the past nearly 20 years... I have dozens of pond owners with trout in ponds that are in that 15-20ft depth range and sustain a healthy RBT population year after year when an aeration has been installed, all of which I have installed and placed completely to the bottom of the pond.

PondPro - thank you. What is the minimum depth you would suggest for a pond with RBT in Michigan? Temps here are about the same.

Canoetrpr,

Give it a shot and see what happens. Trout aren't terribly expensive if you do lose them, so it's worth a try.

And like Pondpro I only know what works for me, and my density of trout is 5000 lbs. per acre upon harvest, so I have to have flow through -- that is-- until I get my coldwater partial recirculation system going.

Keep us posted!

Minimum depth I'd go with RBT would be 15 ft.

Most important feature IMO for trout in ponds is to keep it oligotrophic or a very low nutrient budget UNLESS you have cold water flow through similar to how a raceway functions. The eutrophication processes in static water are what increases BOD and consumes your DO in deeper cold water especially in mid-summer when DO is needed in the depths. This is why quarries with steep banks and deep lakes that are toward oligotrophic can often maintain trout year round. Eutrophication = more productivity deaths & decay = loss of dissolved oxygen = BOD (biochemical oxygen demand) = dead trout even in cold deep water.

Agreed Bill. I can't imagine many ponds even with deep enough and cool enough water being oligottopic enough to hold over trout.

Color me skeptical.

Cody Note: Cecil - You are correct at least considering long term. Many ponds tend toward oligotrophic in early years then eutrophic conditions increase depending on the watershed and external inputs.
Best chances of year round trout survival is to have the pond in an area with cool summers were air temperatures are maximum high 70's or occasionally low 80's and water temps rarely get to 80F. Even then many ponds will still get low oxygen concentrations in the deep water in mid-summer. Best way to dependably raise trout is how Cecil does it by having a small or tiny pond that receives cold oxygenated well or spring water in mid-summer when & after water temps reach 70F. The input of cold oxygenated water throughout the pond serves as your insurance the trout will survive. Trout do not need a big pond. Trout are raised in shallow raceways with cold water flow thru. The current tendency toward warmer climate does not help maintain trout year round. It only takes for a few minutes of low oxygen to dip below 5ppm (mg/l)to kill a trout. For other fish minimum DO is usually around 2.5 to 3 ppm.