Pond Boss Forums AERATION Should I aerate? Aerator stirring up turbidity from lake bed

Any advice appreciated:
I manage an oval 3 acre pond (13 acre-ft volume), max depth 9ft, in lower New York State. There are some fish, but the pond is mostly used for swimming. Currently have 1hp aerator running four diffuser heads (6-9" long silica diffuser stones on each head). The intent is to minimize blue-green algae outbreaks during summer. My rough calcs show I turn over the lake volume more than 2/day.

This year is the first year we installed the system and the aerator heads are sitting on the pond bottom. It's obvious that they're stirring up alot of sediment. While this is an aesthetic issue, I'm just wondering: is it common practice to somehow raise these heads off the very bottom of the pond? If so, what do people use to do this? Maybe tie the diffuser heads onto some old milk-crates and weight them down?

And, is stirring up all that sediment such a bad thing? Would all this stirring somehow promote the muck to be decomposed faster (such that the turbidity is only a temporary thing?)

Many thanks
Theodore

Theodore, I have the same problem with the diffusers kicking up solids from the pond bottom. Pond is very similar to yours in depth and size. I run 6 Kasco diffusers using two aerators in a 3.5 acre pond for some of the same reasons u mention. I have tried several different methods to solve this problem but none of them have worked. I am now waiting for warmer waters to try something different. I have been told I can raise the diffusers 18" off bottom, but that would defeat my purpose and after many attempts of different things tried, I am not sure that would work either. So for now I am waiting and hoping after this winter of pumping air 24/7 it will eventually stop disturbing the loose stuff around the diffusers. If you find something that works please post it up. I bet we two are not the only ones having this issue.

Tracy,
Something you could try that might work. If you got a single unit of soil floc (1 bag of part A and 1 bag of part B) and got in a boat and applied a little around each diffuser, maybe a 10-15 foot circle around each one, let it settle and if you had some left you could even go back in a couple of weeks and do a 2nd application.

soilfloc works better in warm-ish water so you could consider trying it now if water temps are warm-ish, or wait till spring warmup.

I have NOT heard others do this before but I'm only going by my experience. The bottom of my pond is a sand/clay mix and when you rub across it with your boat or a stick you get a plume of sand/clay. I never knew if my cloudy water was from my aerator, or crayfish or goldfish stirring up the bottom. I tried raising my aerator on a plastic tote but like you, never really knew if that helped or if it was one of the many other variables.

I know in the past if I had to push a stick into the ground in the pond to tie off a minnow net it just sunk right in with little pressure. Now fastforward and I'm status post 2 separate soilfloc treatments, one a year ago, the other this past Sept. Even after 1 treatment the bottom has become kind of like concrete. I have to twist and twist to get sticks to penetrate and sometimes resort to a hammer. I also pounded in some fence posts to hold up my seine net and the soilfloc laden sand congealed around them to the point that I could not get them out. I ended up bending the bottoms by wiggling the tops back and forth and still couldn't get them out. Later I had to wade in the pond and took a lot of effort to get them out (they were only pounded in about a foot but the soil floc really packs itself around them and doesn't let water get in to loosen up the particles as you wiggle them back and forth)

You can scratch the top of the sand in my shallows now with a trap or a stick and no plume at all. It is like that sand grout where it looks loose on top of the grout but the particles are almost cemented together.

Since you could easily apply soil floc around your diffusers just far enough to stiffen the sediment around the plume zone, it might be enough to eliminate that variable. I really don't know how much a diffuser can be blamed for stirring up water especially if they are up off the bottom by a foot or so.

Just a crazy out of the box thought.

You could get some large water heater pans at a plumbing supply and fasten them under the diffusers. Or, if you can find an old poultry house not in use, get some 4 ft aluminum brooder hoods and put them under the diffusers.

I'm so far from an expert it isn't funny, but isn't just the fact that the aerators are doing their job by circulating the entire BOW that it's picking up the top layer of sediment? Which as Theodore eluded to is promoting the muck to decompose? Which seems to be an added benefit of aeration.

I'm thinking that even if the diffusers are raised off the bottom, that the "turnover" aeration creates, in some cases more than twice in a 24 hr period, is still going to disturb or stir up the muck even below the raised diffusers? If not, isn't that defeating the purpose somewhat? That we want some disturbance so it can decompose, and that we want ALL the water moving?



I can understand at initial startup how it would stir things up around the diffuser but it would seem in short-order that the area around the diffusers would be cleared, so to speak (at least with a rubber membrane diffuser as I'm not familiar with the silica stones).

Is it possible to over-aerate? i.e., too much water moving or too many turnovers per day?

Just some thoughts.

Keith, yes, I agree with your theory. Problem is that after 5+ months of 24/7 aeration (since this past May), the consensus is that the turbidity has pretty much remained constant. It's actually reduced a little, now that it's gotten colder. One more piece of information: our lake is surrounded by many deciduous trees. So we do have a significant leaf load falling into the lake during autumn, with little recourse to reduce this.

That said, I'm wondering what others (with similar ponds) have experienced. Does the turbidity increase/decrease or remain the same after 1,2,...X years of aeration from the lake bed? Is there no change over time? Just curious what to expect, if anything.
Thanks

Is the turbidity due to suspended sediment or due to algae feeding on the increased nutrients?

I don't think it's algae that's causing the turbidity. At the very least, the blue-green algae we've battled in the past has been well-controlled by monthly copper chromate treatments during hot/summer months.

The turbidity we have witnessed looks dark brown. If I were to guess, it's organic matter from the lake bed being suspended by the aeration process. Any thoughts on whether this will reduce over months/years of aeration? Or... given that there's leaves falling into the pond every autumn, the muck just gets renewed each year?

Could it be phytoplankton?

Get a few mason jars. Fill them with water, cap them, set one in a closet for a day or 3, set the other on a shelf where it gets light. See what settles out or if it stays in suspension.

I have a very similar situation in my pond including a heavy fall leaf load. Has anyone found any of the "muck reducers" in conjunction with aeration to have better results?

That is exactly why I have not pulled the trigger and bought an aeration system for our 6.5 acre BOW (60+ years old). I will certainly see the same sediment problem happening if I put diffusers on the bottom.....or very close to the bottom. Probably a foot of muck on the bottom of my old BOW....that would be a pure guess based on wading the shallower areas.

I need to figure out how to get the diffusers as close to the bottom as possible without disturbing the muck....that is the last thing I want to occur after dropping a good chunk of change on an aeration system.....I don't need permanently cloudy/muddy/mucky water. Maybe the 12-18 inch height off the bottom is actually about right??

Thinking of constructing a PVC "box"....18 inches high....that the diffuser would sit on. Maybe even add some sort of "pan" between the PVC box and the diffuser.

Hope you can find a solution to what has to be a totally frustrating problem millinghill. BM61

When using Vertex diffuser assemblies I have never seen a disturbed sediment problem, even in a pond that is supposed to be 60 years old and has 5' of muck build up on the bottom.

Ask that question again in 12 months. I have 4 ponds that I have measured the muck and just started treating all of them with muck digesting pellets.

I will say yes as long as there is sufficient O2 at the bottom of the pond to allow the bacteria to work. But, this is the first time that I've measured the muck level before starting treatment.

My pond bottom was packed down using large dump trucks full of dirt, so he bottom is fairly firm but there is some clays on the ponds bottom that is getting disturbed by the diffusers. I will see some lightly cloudy water around the diffusers. I started out by setting the diffuser plate on cinder blocks and then on kiddy swimming pools (4' by 12") and also tried the large water heater pans. None of them worked, but it's not that bad, I can live with it but I had never seen it mentioned prior to buying the diffusers. If it continues through the winter I will try something else with a larger base after the water warms up and I can see under water with scuba gear. My thoughts are when I move them for cleaning and reset them on bottom it will all start over again. The best I can tell it does effect the ponds overall water clarity and may reduce the visibility by approx. 2". If I shut it down for a day the visibility will clear up about that much.

I too wondered if there is a difference between your silica stone diffusers which may shoot bubbles in all directions including sideways and down towards the bottom, and the vertex which only shoot air bubbles straight up?

Yes, the silica stone diffusers shoot bubbles out all sides, but they're attached to a manifold, and often the manifold sits on a pvc plate (like this: http://ecx.images-amazon.com/images/I/71kopRSUHrL._SX522_.jpg). So, unless the plate settles onto the lake bed upside down, it won't be shooting bubbles down.

We shut down our system for the winter this past week. When we start up again in the spring, I'll take photos right before and after and a few days after too. I want to get some objective observations.

I am super-interested in hearing anyone else's experiences.