A pond skimmer is a garden pond tool collecting and removing debris from the surface of the water. The skimmer uses a pump in order to draw water into the skimmer to gather the remnants of insects, debris, etc. into a net and the water returns into the pond.
How do Pond Skimmers Work?
Skimmers take advantage of one of the unique qualities of water, surface tension, to effectively clear ponds of any debris that floats, even if only for a short time. The ‘skin’ on the surface of the pond is actually tougher than you might think. Insects like the water strider and water spider walk on it like we walk across the street, because that skin will support a surprising amount of weight as long as it’s well-distributed. As a sheet, it’s also surprisingly resistant to tearing. If you pull on one side of the sheet, you can actually drag the whole surface across large distances. That’s exactly what a well-designed skimmer does.
All skimmers have an opening that allows water in, called a weir, and most have a floating door that keeps tension on the skin of the water by directing most of the ‘pull’ to the surface. A properly designed skimmer matches the pump to the width of the weir. Too little pump or too wide a weir and the pull won’t be sufficient; too much pump or too narrow a weir and the surface will tear; lots of water will pour into the skimmer but little debris will make it across the pond. Stay at the middle of the manufacturer’s recommended range for best results.
All skimmers have some way to collect that debris; how they collect it might be even more important. Look for generously sized nets, mats or pads. The smaller they are, the faster they clog, and a clogged mat or pad might keep water from getting to the pump, leading to overheating and potential failure. The best skimmers have ways to capture debris without starving pumps of water, like brushes that part to let water through even when full of debris, instead of pads that seal off water when neglected too long.
The skimmer houses and protects the pump, so you’ll want one that’s designed for easy pump connection and removal, and that’s easily cleaned when needed. Finally, since the skimmer is usually attached to a hole in the liner, the methods and hardware of that attachment must be of the highest quality. Look for stainless steel hardware, not plastic or aluminum, that clamps the liner to the face of the skimmer securely.
Hiding Your Skimmer – A Simple Technique
Although skimmers have rightfully gained prominence as an essential component in the professionally built pond, there’s no reason at all to show them off. The last thing anyone wants to see at the edge of a beautiful pond is a big plastic garbage pail, and there’s no need to. Skimmer installation doesn’t have to be right in the coping stones at the edge of the pond. Here’s one way to install any skimmer well back from the edge where it can be completely hidden from view.
Let’s assume you’re building a new pond. This technique will only work for retrofitting a skimmer if there’s plenty of excess liner, because we’ll need it to pull the skimmer away from the edge. With a new pond, allow about six extra feet of liner on the side the skimmer is going to go. Often, using a corner of a rectangular liner can give enough extra liner to effectively back the skimmer away from the edge. Let’s also assume that you’re going to be installing the edge rocks on a rock ledge about 8” deep, so the water level can rise and fall 8” without showing any liner. You may already know that this rock shelf is a perfect place to locate bogs, either passive, without pumped water, or active, with water pumped into them. What you may not know is this is also the ideal place to locate a skimmer, back at the rear of the rock shelf 2-3 feet from the edge of the pond!
Here’s how it works: instead of a rock shelf that’s only wide enough for the rocks at the edge of the pond, dig the shelf back, still at 8-10” below water level, but a good 3 feet back form the edge of the pond. Make sure your liner can not only go back that far, but also come up at the back of the shelf at least a foot to be safe. Dig a hole for your skimmer at the back of the shelf, so the 12” that comes up the back of the shelf will cover the face of the skimmer when it’s set at the proper depth. The skimmer weir will end up a good 3 feet away from the edge of the pond. Check that you have sufficient liner, then make sure that the depth of the shelf in front of the skimmer will end up deep enough to cover the liner with a layer of gravel or the rock you’re using and still allow unimpeded flow into the weir. Finally, before installing the liner to the face of the skimmer, leave a little slack in the liner at the base of the weir, just in case there’s any settling. Once the liner has been attached, set your coping stones at the edge of the pond like you would have normally, but leave a channel about 18” wide from the pond edge to the skimmer, lined on either side with the same coping stones at the same height. Create gravel bogs filled with marginal plants on either side of the channel. This little river will allow the plants on either side to completely hide the skimmer from view.