Pond Boss Forums AERATION Systems questions Pond filter for 1/4 acre pond?

Hi, middle TN new 1/4 acre pond, need to find a pond filter or equivalent to maintain clean system/water/etc. What do people suggest? We have an aerator working plus a waterfall under construction which will help w/aeration and circulation. Any advice appreciated. We've already noted that when looking online, most "pond filters" are intended for backyard koi ponds and the like. (Our pond will be ~440,000 gallons.)

Thanks for any advice.

How deep are your pockets?

Typically ponds like yours don't have filter systems, the pond IS the filter itself. Koi ponds have filters that will filter the volume of water in the pond between 1 to 1.5 times PER HOUR. I bet if you spec'd out a filter system for your pond the system would cost multiple times what it cost to build your pond, and then you'd have the monthly cost of electricity to run the pumps.

The only natural water purifiers and water filters in ponds are plants. Aquatic plants absorb nutrients and dissolved substances. When living they pruify the water when dead and decomposing they 'pollute' the water. If you are looking for natural mechinal filtration of pond and lakes it is forms of zooplankton mostly belonging to the Crustacean group named Cladocera. Also freshwater mussels for their size filter lots of water. Zebra mussels filter lots of water but they are considered exotic species and invasive and cause some significant big problems in pond / lake systems.

https://mde.maryland.gov/programs/water/WetlandsandWaterways/Documents/August%201,%202023%20Supplemental%20Briefing%20from%20Waterkeepers%20Chesapeake%20and%20Lower%20Susquehanna%20Riverkeepers/1.w%20MDE%20Draft%20Mussels%20Study.pdf

Mussels are well-known for their ability to filter water. Mussels are filter-feeding organisms that remove particulate nutrients (seston) from the water column. Particle filtration by mussels range from 0.50 to 3.7 Liters per hour per mussel. The Eastern Elliptio is estimated to filter 16.5 gallons of water per mussel per day (24 hours). Through daily feeding activities, mussels improve water quality by reducing nutrient transport in riverine systems. Nutrients taken in by mussels are either stored in the tissue of the mussel (soft tissues and shell material), translocated from the water column to the substrate in the form of biodeposits (feces and pseudofeces), or returned to the water column as excreted (soluble) nutrients.

Assimilation of nutrients in mussel tissues Mussel tissue is composed of 8-13% Nitrogen (N) and 1-4% Phosphorus (P). Mussel shell is composed of 1-2% N and less than 1% P. A single mussel is estimated to contain approximately 0.7 g N and 0.009 g P.


Video example of filtering ability
https://www.instagram.com/minnesotadnr/reel/C3z8WjgPwEe/


Harnessing Mussels to Filter Fresh Water

https://www.greatlakesnow.org/2024/08/harnessing-mussels-to-filter-fresh-water/

The way it's been explained to me is that we need to have the water "moving." Ponds with other water sources such as a stream, etc. have natural filtering that way....we just have a standing pond. There is a nearby pond that is similar size, also standing pond w/no stream, spring, etc. that doesn't look all that great, and it is often full of algae, etc. Another nearby pond same thing. I would note however, that those ponds are not particularly well maintained in general; the owners are fairly disinterested.

Algae is present because of excess nutrients.

Basic summary is a pond without a flow through is a big bathtub with no drain; a toilet with no flusher. What gets in or is put in stays in. If that stuff decomposes it releases nutrients. Ponds collect nutrients in many ways to grow more, usually more plants of some sort. How are those nutrients supposed to get out of the pond?. Answer - something that grew in the pond has to be harvested out be it plants, fish, animals or organic materials that blew in or rinsed in, or bottom sludge that has nutrients. Ponds are collection basins that become more enriched each day and year. Nature by a process called aquatic succession works to fill the pond back to a swamp and then dry land.

Understood. I have an aerator working, soon will have the waterfall (with pump) as well. Since I want this to be a swimming / fishing pond (in that order of importance- I've been told if you say "swimming pond" that's what that means), so nice clear water is obviously a priority. This has probably been explained to me already (maybe more than once), but please indulge me by telling me the best way to achieve what I need. Thanks!

"Best way" is in the eyes of the beholder. Look into biological filters for swimming ponds. The ones that I have seen are approximately the size of the pond, aren't very deep but are filled with plants. A pump takes water from the swimming pond and pumps it into the biological filter, It runs the length of the filter and dumps back into the swimming pond.

That takes out the majority of nutrients that contribute to growing phytoplankton, which is the bottom of the food pyramid for the fish in the pond. What you are trying to do is make a 440,000 gallon aquarium that you can swim in. So, that means physically feeding the fish and not letting things grow in the pond that will feed the fish.

Nick,

I think the idea you are looking for goes by many names: swimming ponds, living pools, natural pools, etc.

There is an entire culture of people that do your idea at their property. IMO it is mostly DIY since it is rare enough that it would be difficult for a full-time contractor to make a living doing ONLY that type of work.

The link below shows some excellent examples of the concept and also explains the fundamentals. Once you get the gist, you should be able to search for many more source articles.

Natural Swimming Ponds

I have researched this type of pond for our property, and did wonder if it could be optimized by adding some filter-feeding fish. Would tilapia or threadfin shad make that type of pond even more clear?

I think the strength of Pond Boss is the available expertise on "fish ponds". If you get really serious about the project, maybe start a new thread and ask the experts about deliberately adding filter-feeding fish? I don't believe either TFS or tilapia are known for nipping at swimmers.

Good luck on your project!

FishingRod, the true filter feeders (like paddlefish) would starve to death is a clearer water pond.

Would any of the fish like TFS or tilapia (or any others you can think of) be helpful in this kind of "water clearing" application?

In my area, I would definitely want to add some gambusia to eat up the mosquito larva and other similar-sized zooplankton/larva. Without a "minnow predator" in the swimming pond would there eventually be a billion gambusia, or would their population remain reasonable as they ate up their own food supply? If needed, add one LMB or SMB to the pond as a minnow predator?

Any expert advice from our "fish pond" experts would be greatly appreciated!

I remember growing up occasionally swimming in fresh water lakes, and how exhilarating it was. Places like Lake of the Ozarks, where my uncle had a cabin......it was heaven. No one would call that a "swimming pond", but the swimming was sensational. And other lakes, those places were full of fish. So honestly, I have to say that what I'm looking for is just the cleanest, nicest water it's reasonable to have. That's all. I realize I'll have to compromise....I'm already seeing that compromise is a big part of having a pond; you can't have everything perfect.

Note in the link for Natural Swimming Ponds they emphasize harvesting each fall the marginal and emergent plants that grew each year to help clearify and improve the water quality. This gets back to what I posted earlier. HAVREST from the pond, be it anything. All types of harvesting stuff from the pond is very beneficial at reducing nutrients because excess nutrients do cause eventual water quality and water clarity issues.

The freshwater lakes of the Ozarks that you describe have lengthy shoreline areas and littoral zones where marginal and submerged plants grow absorbing nutrients that compete with cloudy water causing phytoplankton blooms; plus the Ozark lakes were not overloaded with nutrients and tend to keep water blooms to a minimum. Algae blooms are ALWAYS a sign of over nutrient enrichment. Truth be known Lakes of the Ozarks assuredly have/had low nutrient inputs, lots of good water filtering zooplankton and freshwater mussels that help filter suspended particulates from the water. Overloading a pond or lake with nutrients is the big problem that causes green water ponds or conditions. IMO the more nutrients that a pond receives,,,,,, means more stuff from the pond that needs to be harvested IF good water quality is one of the main concerns or goals.

Keeping nutrients low or minimized in the pond is important to maintaining a clear water pond as also was emphasized in the link for Natural Swimming Ponds. Low nutrients are a big requirement for clear water ponds. Also the right kind/s and numbers of fish that allow good water filtering zooplankton to flourish are also very important for having a clear water pond.

Maintaining clear water is all about nutrient management. Amen

Thanks for this. Such ponds are lovely and inviting, but honestly, this is absolutely NOT what I'm looking for. I just want to have a nice pond and be able to swim in it! I just don't want a murky, yucky pond that no one would care to jump in. I understand everything is a compromise.

This touches on an issue I have been thinking about for a while. If the water replacement rate (or the differential nutrient content of inflow and outflow water) is insufficient to keep the bathtub at some equilibrium, it seems that the only other recourse is to actually intentionally harvest nutrients from the pond. Even when you just clear out vegetation, unless you move that debris out of the watershed, its nutrient content will eventually return to the pond through surface or ground water leaching or suspended transport. Even a filtering pre-pond has the issue that unless you periodically remove waste organic matter, those interrupted nutrients will eventually get back into the pond.

The primary way of removing nutrients that interests me is to harvest high on the food chain (fish) and have a small garden to use the fish remains to grow edible crops. I guess you could compost any harvested aquatic plants to provide nutrients for a food garden.

The problem I have is quantifying the likely net nutrient input. It is relatively easy to find the nutrient content of fish that are harvested. But identifying the primary input sources (I think in my case forested surface water runoff and leaf liter) seems to be largely guesswork.

For reference I have a new (2 yr) 1/4 acre pond in a forested rural area near the Cuyahoga National Park in NE Ohio, constructed from a natural bog (no dam) in a headwater area.

I just took water samples from 2 different customers ponds to get the water tested for nutrient levels. If input nutrient levels are known, water exiting the pond can be tested for nutrients too. BUT you have to remember that different times of the year will have different nutrient levels entering and exiting the pond.

My philosophy about nutrient removal is harvest as much as feasable and possible for your situation. It is doubtful that you will be able to remove as much or many nutrients that nature and you put in or allow in each year. Some harvest is ALWAYS much better than no harvest.

In general, the natural swim ponds require at least 1x the area of the pond as a “wetland”, full of plants and a few feet of gravel. Water is slowly pumped through it to utilize the surface area of the gravel for hosting bacteria that do the cleaning, and the roots of the plants that uptake the surplus nutrients.

I wish I could do this, as one of my pastimes is gardening. But my hillside pond and distance to power make it prohibitively expensive.

The other aspect is you will lose a lot of water to evaporation in these systems. You will likely need to near constantly add water.

You may find that your pond is perfectly good for swimming without doing anything for the first few years until it hits a point at which the nutrient level supports unwanted plant growth. You can extend this time by not feeding fish, and making sure leaves stay out. Also do not fertilize lawns around the pond or allow farm runoff to enter. Also it can be lengthened by adding desirable plants like lilies, and in my case allowing cattails to grow where I normally have inflow to block leaves and sticks from getting in.

Another option is floating island planters. I forget who on this forum was doing it, but it is a clever way of pulling out excess nutrients.

B.cody note - Liquid is give very good advice - heed it.

Lots of good ideas here. Some would be difficult, such as the "wetland" idea....not practical for me. But some of these are easy: not fertilize lawns, add lilies, etc. Not cattails in the pond; I've heard nightmare stories of them taking over.....but my contactor has ideas of using them in a separate area w/ water runoff near the pond....he's explained it but I don't grasp the full idea.) Also, when the pond is full, my plan has always been to have a couple of "chinampas" out there- that's the Aztec word for floating gardens, and plenty of people I see on YouTube are doing this....had no idea it would have the fringe benefit of aiding in "pulling out excess nutrients."

This hits on something I've been thinking a lot about lately, along with my contractor/friend: using the pond water/fish/by-products/all of it to enhance my garden. I grow over twenty types on peppers as well as herbs and other things. I would far prefer to use rainwater or pond water rather than city water. And I want to utilize as much natural products (I make my own big batch of compost every year; things like that, including vermiculture etc.) so anything I can do to tie the pond into the gardens etc. will be highly preferable for me.

That sounds like a good plan!

How far is it from your pond to your plants?

If too far for direct pumping there are several easy "cheats" for you to use.

I have a cheap 12V DC sump pump that I throw into my ponds to fill a tote on my truck. I power it for a week or two with just a single deep cycle battery. That pump gives me a quick 275 gallons to drive around the farm and water saplings during dry conditions.

I have also had great luck with the drip irrigation systems. They do need a little bit of head (pressure) to operate efficiently. I just put my tanks on 4' high platforms. At that elevation even the drip emitters and the end of the line deliver water at the design rate.

The only drawback for me: If I set the rate too slow, then algae will form in the tank and plug the emitters. For a full garden and quick tank drainage, I don't think you will have that problem.

Wow, I thought I already responded but don't see my post...?? Anyway, I mentioned that my contractor refers to the pond as a "bathtub" as well, reminding me we don't have the luxury of natural inflow / outflow, so we need a setup to avoid algae, etc. buildup. btw: pond is only 60-70- ft. from the house / garden area / shed / compost bins / etc. so we're going to have a convenient hose setup and we should be good. Thanks for your response.