Answers to Pond and Water Garden Questions

Q. The hole for my garden pond is ready for the liner, but I need some form of underlayment because of the rocky soil. The home improvement center sells a very thin product for this, but I am not convinced it will do the job in my situation. I have access to plenty of used shag carpet and have read that this can be very effective as underlayment. Any tips on using carpet as underlayment? My concern is that its bulk will make the task very difficult. My pond is kidney shaped and about 8 feet by 5 feet with a shelf all the way around.


Positively, use the carpeting. If you cut the carpet down to 2 1/2 or 3 feet strips you will be able to handle it easier. Just make sure there are no tacks in the used shag you have. The liner is big enough; dig the pond even a bit deeper than you planned.

Q. I hear that if you use barley straw in a pond it will help control algae. Is this something I could use in my small backyard pond and will this harm my fish?

A. Barley straw is supposed to help reduce string algae. Not sure why it works, it may have something to do with adjusting the pH of the water. String algae seems to like the water at a higher pH of 7.8 + (or maybe the bacteria that help control the algae cannot cope in water with higher pH). Calcareous rock (limestone based) will tend to raise the pH of the water. You should be able to use it in your backyard pond. It does not start to work until it starts breaking down.

Another thing you might want to try if you do not want to spend the big bucks on the small bundles of barley straw at a pond store is to stuff an old sock with peat moss from your garden store. This will have the same effect to lower the pH if it is too high. You can test for pH with a pool test kit from your local big box store. Barley grass works and it is inexpensive, as you only need to replace it every six months. But there are dangers.

Now let me tell you what not to do. Do not believe the articles that tell you to tie it to a plastic bottle and then attach it to a rock and put it under the waterfall. This will keep it from lying on the bottom of the pond. Yes, it does keep it floating and floating and floating right into the skimmer. Put the barley straw under lava rocks in the waterfall. It will not break out of there and it will work very well. If you do not keep that barley down, at least keep a sump pump close by.

Q. Are there any aquatic plants that can oxygenate enough water to avoid a pump? If so, what are they? If I go this route, what happens in the winter, will the plants freeze or die? In general, what are some good starter plants for a fishpond?

A. Why not run permanent buried GFCI lines to the pond? This way you can run a filter, WF, and add oxygen with an aerator, if needed. Most hardy pond plants need to be lowered to the deep part of the pond to avoid being frozen out. Oxygenating plants in your size pond are probably not enough to support the fish. Skeeters can be controlled with "Mosquito Dunks." Smaller fish will also consume the larvae. A good starter plant is water lily - to shade the water, keep it cooler and lessen algae. A couple of oxygenates are anacharis, and elodea.

Q. Can someone tell me what type of rocks to use around my pond? I will need to cut them to different sizes - which type is easiest to cut?

A. The type of rocks you decide to use will depend on a number of factors. Cost is often a major concern. Why pay $40 or $50+ per ton if you can harvest some locally? Also, the physical characteristics of the different rocks would be important. Are they smooth or jagged? Can they be easily shaped? Do you want to have a layered effect or more of what you would find on a fast stream's bed?

One other thing that you might want to take into consideration would be what the rocks actually are. Granite rock is pretty much pH balanced, but most limestone or calcareous rocks will cause the water pH to go up or sour. Many plants and fish will not thrive as well when the water pH goes much beyond 7.6 - 7.8, so you might have to use peat or sphagnum to acidify the water a bit and bring the pH back down to more ideal levels. When cutting rocks, most sedimentary rock will cut easier when you follow the grain in the rock. The harder materials like granite and hard shale usually will shatter in places you do not want while the softer limestone and sandstone are more controlled when using a hammer and chisel. If you are going to use a diamond blade or wet saw, either type should cut in a more controlled fashion.

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