Q. I recently bought a house with a small natural pond in the backyard that is fed constantly by a spring. The pond is filthy and sludgy looking. It also looks like the homeowners put in a soft pool liner under all that sludge.
First of all, is there an easy way to remove this muck? Would it be best to try to drain the pond and just remove the liner and install a new liner? Honestly I do not know how this can be done because the water is always flowing. Once the whole pond is cleaned out, is there a way to assure that this dirt and sludge does not accumulate again? I did not know if there was a cleaning or filtering system for natural ponds or not.
A. Since the pond has a liner, it is no longer natural. Natural ponds have muck in them, and adding plants and rocks may help keep the muck in place and keep it from getting stirred up. Marshy areas chock full of bog plants or marginal also act as a natural filter that should promote settling of solids and clear the water. Clean out as much of the muck as possible and then try to locate where, exactly, the spring feed is. It could just weep up throughout the entire bottom of the pond; that is not normal, but could happen.
Try to "control" or seal the bottom of the pond with a natural surface, maybe sand or clay. Keeping in mind where the spring feed is because the water will come up whether you like it or not, so do not try blocking it off or it may come up where you do not want it to.
Next lie in a pebble bottom and work your way up from there. The clay or sand should seal off the remaining muck, and now all you have to worry about is keeping the muck out from above. The sand may also act as a natural filter for the bubbling spring water. The first thing you need to think about is getting that muck out. This will require you to drain your pond. You will need to divert the water somehow for a few days while you are working on the project.
Now that the pond is empty, clean it out all the muck and weed plants that you do not want. If you want to save plants, you will need a temporary nursery. The problem you are having is called a giant settling pool. To get rid of this gunk that settles in your pond, you need to install a "bottom drain." This is located at the deepest part of the pond, and you might need more than one. A bottom drain consists of a screen of some sort so as not to clog your pipe. This drain will be your new outlet for your pond. It is than connected to a 4-inch pipe, or whatever is cheapest or sufficient enough to handle the capacity of water coming in. You want to completely change the water in a pond about two or three times an hour for nice water. Run your pipe the way that the pond is naturally flowing now - up over the rim and down the watercourse.
So your checklist includes redirect water, clean out muck, figure out your inlet flow, match pipe to keep up with flow, install bottom drain, now siphon away! You can also have an overflow if there is a lot of water, but if the bottom of your pond is sucking from siphon pressure, you will be a lot more muck free.
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