Pond Boss Forums GENERAL QUESTIONS Water chemistry What Chemistry for clearest possible pond?

Hello All:

I am in the process of digging an approx. 1/3 acre pond. It's main use will be for swimming. In fact, I am not even planning on stocking it.

It got me to thinking about what kind of water conditions I should strive for, since I will not have to worry about supporting fish.

I guess my goal is maximum clarity. I would like to create conditions that deter phytoplankton and algae as much as possible. I am considering planting desirable water plants in shallow parts of the pond, but only for the goal of taking up nutrients that make their way in. I live in NH, so our ground pH is naturally low.

I guess by focusing on the chemistry, I am kind of going about it backward, but in a good way. Be deciding what kind of water I want, I can work back and try to figure out how best to get it. How should the pond be designed? What should be planted and where? Etc.

And advice you have would be greatly appreciated. Thank you.

Backstroke

If it is to be used mainly for swimming (no fish, turtles or water fowl), it should be heavily planted with diverse species of plants. This will assure the water quality that you seek.

Thanks, Instar. I have heard positive things on the forum regarding planting in pots, and then submerging them. Or given my goals, would I be better off to let them take off and spread?

Backstroke

Plants in pots will not develop enough biomass to adequately deplete enough nutrients to keep algae reduced. IMO plant the plants in the pond bottom. Choose low growing or short plants that are endemic to soft low alkalinity water similar to where you live. I would get most of the plants from your local lakes. Research Isoetes lacustris (lake quillwort) and similar species and Dwarf Sagittaria (Sagittaria subulata) for submerged plants. Dwarf and small varieties of hardy hybrid water lilies will be your good pond plants. All plants will spread some fast some slow. Pond plants will need thinning and weeding similar to a flower garden.

No fish = mosquitos and lots of biting backswimmers/water boatmen. Maybe consider at least stocking some FHM [control mosq lavae]and single sex BG to manage the backswimmers and boatmen. Few dozen FHM would do the trick, and probably a 20 BG.

I second what TJ posted, but be VERY, VERY sure about the sex of the BG. There is very good information in the archives on how to tell the sexes apart. If there is ANY doubt whatsoever, don't stock it. Just FHM won't do it. A client has a small pond that he uses for raising forage fish, and it's only stocked with FHM and some Papershell crayfish (well, there's 6 Pumpkinseeds in there too). There is a huge population of water beetles in the pond, but I haven't noticed any mosquito larvae.

I have seen a few ponds for just swimming and though I haven't talked to the owners this is what I have observed. The sides of the ponds are steep and lined with rabble rock to keep any vegetation from growing. Also the ponds are heavily dyed to keep the sunlight from penetrating the water to suppress weed growth. Weather anything else is used in the ponds I don't know. A friend has a one-acre pond with a spring diving board and he uses for swimming. He has fish in it and uses copper sulfate to keep down the FA. I don't know what else he uses for weed control but he has only low growing plants in his pond and does use some dye but doesn't have the steep banks and rabble rocks.

Thanks, TJ. Definitely a concern. I was wondering if the frogs and salamanders would take care of things, instead of fish? And if I kept the pH pretty low, too low for fish, if that would also help with mosquitoes and algae? Just wondering.

Backstroke

Hi John, and thanks for replying. I guess the above method is kind of the opposite of the approach Instar and Bill suggest:





Maybe both are different means to the same end. All things being equal, I prefer the more natural approach, and letting the various cycles do their thing. Plus given that we hit ledge at the front of the pond (where the surface water will enter, this will end up being a naturally more shallow area. This may be wishful thinking, but if I turned that section into a planted area, it would catch the debris and nutrients before they move beyond into the deeper section.

And I don't mind Bill's scenario of weeding it like a regular garden. We sure do enough of that already.

My assumption all along has been to aerate. Does anyone think it would be counterproductive, given my goals?

Thanks again to everyone who responded.

Backstroke

It is difficult to maintain a pond as a clear water swimming pool. I have several ponds used mostly for swimming and domestic water use near me that have water visibilities that commonly range from 8ft to 18ft. IMO one of the biggest problems will be the muck and dead organics accumulation on, in, and among the gravel bottom, sand or sediments.

Firstly I don't think you can decrease the pH and maintain it consistently low for long periods, at least a pH too low for fish survival.

Secondly TJ is correct: "No fish = mosquitos and lots of biting backswimmers/water boatmen". Mosquitos can be pretty well controlled by dragon fly larvae and adults, but water boatmen and back swimmers are another story. I've seen water boatmen and backswimmers as dense as 1 per quart of water in fishless ponds. Supposedly the water boatmen do not bite but both have piercing mouth parts. Whirligig beetles on the surface can make some swimmers shy to enter the water. They can bite if handled.
http://beneficialbugs.org/bugs/Whirligig_Beetle/Whirligig.htm

My recommendation for smaller (0.1-0.5ac) swimming ponds has always been to add a few smallmouth (SMB)or largemouth bass(LMB) (10-30) and forget about any other fish. I prefer SMB because they thrive better on a mostly 'bug' diet. The bass: A. will not get big (7"-9" maybe10"), B. will not bite swimmers, C. do not need to be fed, and will keep the bugs, crayfish, tadpoles, and small critters controlled. The adult bass (8"-10") do not eat the larger zooplankton, mostly Daphnia, which will keep the water generally clear unless the pond gets an excess of nutrients from watershed, leaves, waterfowl or feeding fish.

Pictures of your pond project show trees fairly close to the pond - a big concern for me because of annual tree leaf inputs which introduce organic materials that make muck and dissolved nutrients which grow algae. Tree leaves are a big problem for pools and ponds. Pool owners skim leaves and large organics daily. Algae as phytoplankton or filamentous will be low or sparse as long as you can keep nutrients and organic inputs at a low concentrations. If the pond water has low alkalinity this will also help keep algae less. Secrets to keeping clear water in a pond are low nutrient concentrations and some rooted vegetation to utilize what nutrients are present. You will probably always see a little bit of filamentous algae. Large amounts indicate way too many nutrients. Although large amounts of filamentous algae generally causes clear water conditions due to binding lots of nutrients and starving phytoplankton. Harvesting some plants each year helps keep the nutrient budget low. The more plants including algae that you can harvest each year the less the filamentous algae that will grow. Filamentous algae only grows on the excess dissolved nutrients not utilized by other plants (phytoplankton and or rooted).

Bottom diffused aeration helps keep the water clearer, fresher and helps speed the decomposition of organic materials such as dead plants on the bottom. In NH proper sized aeration will not need to run 24/7 to keep the pond in good balance with clear water as long as you provide 1 to 2 turnovers per day in a small pond which could take 4-6hrs.

Dear Bill:

Thank you for your thoughtful and detailed response. I will incorporate all of your suggestions into my plans. Bass it is. Do you have an inclination one way or the other regarding small mouth or large mouth?

By designing the main inflow carefully (rock as well as grass barriers),I hope to keep the influx of organic matter to a minimum. I
will keep mowing to a mimimum, both above the pond and along the sides. I will not fertilize uphill of the pond, nor along the sides. And we have already and will continue to remove trees as the pond grows. The trees that are left will certainly release leaves that will end up in the pond. I have not researched skimmers, but if you felt skimming to be beneficial, I would certainly look into it.

I will introduce plants for the reasons you stated. In an earlier post, you mentioned lake quilwort, dwarf sagitaria, and hardy dwarf water lilies. Will these three be up to the task, or are there other varieties you suggest that I introduce?

And thank you for verifying that I was on the right track regarding aeration. I posted my situation and got great feedback in the aeration systems section regarding how best to do it and what equipment to choose.

Thank you again for the time and effort you have put into analyzing my situation. Your recommendations will be followed and I will keep posting with my progress.

Backstroken

Bill recommends "SMB" in his post ... smallmouth bass.

If given a choice I always prefer the smallmouth bass for swimming ponds. Although largemouth work okay for many swimming ponds in my area. The only down side to using the bass that I've found is they eat a lot of the tilapia babies and it is the army of tilapia baby fish the eat the most filamentous algae for the owners of a swimming pond. So we have been dramatically reducing the bass numbers by harvesting in the swimming pond.

Windblown leaves will be your biggest problem. It is for ponds in my area. Reducing fertilizer usage on the water shed is critical. Look into buying an extendable handle smelt dipping net with 3/16" to 1/4" mesh. It is a great leaf skimmer. The one that I use has an 11ft 3in handle and overall length of 13ft. Anything else you can use to remove leaves before they sink will be very beneficial.

Those are the three best underwater pond plants that I know of for swimming applications. They will not spread fast which is a pro and con. To get more quicker benefit, plant more in more areas. Be advised that ducks, geese, and turtles will want to eat your plantings. Discourage them until plants are well established. If your homework and discussions with other natural swimming pond people arrive at other pond plants, check with me for a 2nd opinion of pros and cons before planting.

The pond when new with small planted areas will often have its fewest or lowest nutrients of the annual nutrient budget of the pond. From year one, more nutrients are constantly accumulating due to annual inputs, thus more plants want to grow. The trick is to channel the growth into beneficial low work plants. Often new ponds will get a surge of filamentous algae growth. It is best IMO to allow it to grow, eventually float and remove it and its absorbed nutrients with the smelt/algae/leaf net. Killing the algae in the pond sends the biomass and nutrients to the sediments to be recycled for more plant growth later.

Thanks again Bill.

I was wondering if there were any opinions on my idea for plant placement. As I understand it, the plants I am striving for will not grow in deep (over 6') water. So that leaves me with a couple of options at this point.

As you can see, my pond has a naturally shallow section due to ledge that could not be removed, and a section that was free of ledge that was excavated quite deeply:



By sheer chance, the section of ledge is where the majority of surface water will be channeled:



So I can use this section exclusively for water plants, leaving the other slopes somewhat steep. Or I can ease the slopes elsewhere and try to create more shallow areas for plants.

One advantage of having lots of plants clustered where the surface water enters is the potential benefit of having the plants filter the incoming water before it heads to the rest of the pond. But will this be enough planted area? Will it be too concentrated? Will proper aeration cause enough of a mix of nutrients that one heavily planted "plant station" will cast its benefits throughout the pond?

We are getting closer to completion, so if I need to incorporate more area for plants, I had better do it soon.

And given the varieties Bill suggests, is there an optimum depth for these species to thrive? What should be my goal, both over the ledge and if necessary, in other sections, for water depth for best plant results?

Thank you all again for your invaluable advice.


And HEY! I think I finally have Photobucket figured out, thanks to F n' C!

Backstroke

Another thing you can do to prevent some windblown leaves from entering the pond is to put in some fence upwind. This will allow the majority of leaves to drift up along the back of the fence rather than entering the pond. If you have a lot of rocks, you can build a relatively tall stone wall, 4ft or so upwind from the pond to serve the same function, only much more attractive.

Bill C is giving some great advice! Thanks Bill.

I didn't build my pond originally for swimming, but it has become a great swimming hole mostly due to dumb luck.

From your pictures it looks as if the rock dock is too low? Remember bare feet as well, so a smooth surface would be nice. Also a steep drop on the very end for jumping/diving or ability to place a ladder. I found an aluminum 5-step dock ladder worked pretty well in my pond as it conducts heat from the lower warm water to the surface which except on the coldest days kept the ice off of it. Our ponds are too small to have ice heave the docks and ladders.

Whirlygigs do bite by the way, they are devious little jerks. Usually they nip when you are working on something and both hands are busy and cannot shoo them away. Painful bite, and they latch on! I may have to toss in a single SMB if they eat the whirlygigs. Nothing else seems to, I have thousands of them.

Great idea on the fence, liquid. I may tweak that a bit and try to go with bushes so it looks more natural. But a substantial physical barrier is a great idea. You are right about the dock, liquid. It is "in construction" and should have another level added so that it just protrudes from the water. I may have to wait and see what the final water level will be before the final tweaks.

Any ideas on my "plant zone" would be greatly appreciated. They just pulled the big excavator from the site, and the other equipment will be going soon. So it is crunch time for any last things I should get done.

Thank you all for your continued support throughout this project.

Backstroke

Plant the plants shallow 12" to 2.5 -3 ft deep. This assumes the pond water level will stay full. Plant some even along areas of your steep slope on opposite shore of the stone ledge. They will colonize to depths and areas that they find suitable for growth. If you product clear water with visibilities to 8ft there will be enough penetrating light for plants to grow to 16ft deep. Usually it is at least 2X the visibility or Secchi disk depth.

Will do, Bill. I will find good plant sources over the winter and have a bunch ready to plant in the spring. Along with those SMB.

I was planning to aerate. Is there any benefit to starting to aerate now, or should I start that in the spring too?

As always, thank you very much for your advice.

Backstroke

Spring is plenty soon enough to aerate a new pond. If started in early spring when surface water temps are 48F-52F you will not need to use the gradual or slow start up procedure to begin aerating because a new pond has not had enough time from winter to summer and accumulate high amounts of dead organics (usu years) to develop a strong thermocline with associated anoxic water in the deep zone. When the water gets from 64F-70F that is a different story and aeration start up should be more gradual.

Thanks Bill!