Most folks agree a fish pond would be an attractive addition to the garden but worry about how much pond maintenance it will require. We’re going to talk about how to build a pond that’s as low maintenance as possible – not “No Maintenance”, because there is no such thing. Debris blows into ponds, aquatic plants shed leaves, stalks and flowers, fish turn food into “organic fish emulsion”, so to speak – and it all has to be dealt with. The good news is, most ‘chores’ can be simplified, even eliminated if we design for low maintenance from the start. Let’s look at building a pond to:
• make it easy to keep the water clean and clear without chemicals
• inhibit the growth of string algae and green water naturally with aquatic plants and bog filtration
• keep mosquitoes from being able to breed
• discourage wading predators, like raccoons, herons and egrets
• and most of all, be easy and safe to maintain
How do you Maintain a Small Pond?
In order to build a low maintenance pond, you need to choose the right components, such as pond skimmers and pond filters. You also need to choose the proper location for the pond, dig it out the right way, and pay attention to various aspects such as lighting, aeration, bog filtration and similar.
The Components that Make It Easy
The heart of the pond, pond pumps circulate life-giving oxygenated water throughout the water feature. Without circulation the water can turn stagnant and foul; without oxygen, decomposition can release methane and hydrogen sulfide, smelly and dangerous! Matched with the right pond plumbing, a pump that circulates all the water in a properly designed pond once an hour will eliminate these concerns. Submersible pond pumps are the most common because they are easy to install and hide, quiet in operation and simple to maintain. Keep them clean and well-submerged – or else! – and most will last well past their warranty periods.
Pond skimmers reduce maintenance by collecting floating debris before it can sink to the bottom of the pond. Unlike a pool skimmer, pond skimmers have large mouths capable of pulling in large leaves, and generous nets or baskets that hold plenty before needing cleaning. The pond skimmer is also a great place to house the submersible pond pump: it’s easy to get to for cleaning and service; it’s protected from clogging behind the net or basket; and it’s off the bottom, away from debris which could clog the inlet, a major cause of pump overheating and failure. Pond skimmers work best as huge pre-filters, keeping water flowing into the pump. However, many have optional filter mats which can help filter pondwater. Bear in mind using a skimmer as a filter comes at a maintenance cost. Clogged mats can block the flow of water to the pump, which can lead to overheating and pump failure. If mats are used they must be kept clean, or simply removed when not needed.
The best pond filters are biological filters that both physically remove suspended solids that cloud water and grow beneficial bacteria that convert toxic ammonia from wastes into benign nitrates. A perfectly functioning ‘biofilter’ will clear and detox water, turning fish wastes into – tada! – plant food. This helps explain why algae problems are so common, and gives us a way to suppress algae using aquatic plants in perimeter bogs – more on that later. Water from the pump enters the bottom of the biofilter where heavier particles settle out, then passes upwards through filter mats and media that ‘nitrifying’ bacteria colonize, exiting clean and pure from the top of the filter. Talk about low maintenance – these filters usually only need cleaning once a season!
Last but not least are pond liners that create the waterproof enclosure we take for granted. At 45 thousandths of an inch (“45mil”), synthetic EPDM rubber liner makes the perfect pond liner, supple and elastic enough to conform to irregular surfaces and contours, puncture-resistant and strong enough to handle wear and tear against rock and stone, weatherproof and sunlight resistant. These four main components work together in pond kits to make building a pond as easy and low maintenance as possible.
Where NOT to Build – High Maintenance Locations to Avoid…
Rather than talk about the perfect spot, let’s go through where you DON’T want to locate your pond. Try to avoid siting your pond:
• Under trees. Obviously, ponds that constantly fill up with leaves are a maintenance nightmare, even with a skimmer.
• That low area in the yard. It may look like the perfect spot, but the lowest spot is the worst place to build a pond because of runoff, which can wash away stones or fish, or wash in fertilizers, herbicides, pesticides and silt.
• The sunniest spot on the property. All sun, all the time can promote algae blooms and string algae. Afternoon shade helps with algae control and can keep the water cooler. Cooler water holds more oxygen, never a bad thing.
• The shadiest spot on the property. Full shade isn’t ideal either. Plants like water lilies need at least 4-6 hours of sun or they won’t flower at all, and the water will take forever to warm up in the spring, slowing plant growth to a crawl. Plants use up nitrates and starve out algae, we want them to grow well, in the water and in perimeter bogs. Morning and midday sun with some afternoon shade is the best scenario for most ponds. As in most things, avoid extremes.
CRITICAL POINT! – Before finalizing the location, call your local markout service or dial 811, anywhere in the country, to have your utilities marked out. It’s fast and it’s free. Cutting cable and phone lines is a costly nuisance, but you MUST make absolutely certain you won’t be hitting a gas or electric line. Not only could it save you the major cost of a utility repair, it could save your life.
Pond Building for Lower Maintenance, with the Rock Shelf, Vertical Sides, Plant Shelf (RSVP) Profile
An RSVP Profile is a simple way of building a pond to complement the low maintenance pond supplies in the pond kits. A level rock shelf supports the coping rocks all the way around the pond. The shelf is set 9” below the ‘normal’ water level, so water level can drop 9” and never show liner. The shelf can be narrow enough for just the stones, or wide enough to accommodate perimeter bogs behind the coping. From the rock shelf there’s a short straight drop (the “vertical sides”) 9” down to a wide, level plant shelf 18” below water level. This simple method of pond construction offers many advantages. The vertical sides and knee-deep shelf all the way around, with no slopes or shallows, mean you can easily step in and out onto the flat Plant Shelf for maintenance. Fish and circulation reach everywhere, no stagnant shallows for mosquitoes to breed, or string algae to grow. The 18” depth is good for waterlilies and other plants that help keep water clear by shading and starving algae, but it’s too deep for the most common wading predators, like raccoons, herons and egrets, that need a shallow step to get in and take fish. Building a pond with deeper sides helps keep the water cooler than shallow shelves would, and cooler water slows the growth rate of algae – less algae means less work for you! Finally, there’s greater total water volume in ponds with vertical sides, so ponds tend to stay cooler longer into the warm season, and they stay warmer into the cold season. The cooler water carries more oxygen in the summer and the more oxygen the happier the fish will be. The relatively warmer water in freezing climates reduces cold stress on the fish, and the less stress they’re under, less stress you’ll be under.
How to Dig the Low Maintenance Pond?
Now let’s outline how to build a pond in detail.
• Before you dig: check with your local Cooperative Extension or Koi Club for the minimum recommended depth for your area. Draw out your design on a piece of graph paper to scale, side view like the drawing below, so you don’t forget the liner needed for the shelves. Round off the shape you choose, avoiding sharp points and deep hollows. Design your pond with the pond filter at the far end of the pond from the skimmer for good circulation, and leave a little extra liner for a waterfall coming out from the pond filter.
• Start from the center and dig outwards to take full advantage of your liner. KEEP CHECKING YOUR MEASUREMENTS – it’s hard to undig. Dig vertical sides down to a flat bottom. You’ll want the water’s surface about 4” deeper than the surrounding area, and you want your Plant Shelf to end up 18” deep, so find the lowest point around your excavation and dig your shelf down 22” from that spot, then make the bottom level from there.
• If your pond will be deeper than 18”, dig a second inner level stepped or sharply sloped down to your final depth, leaving 18” all the way around for the Plant Shelf. Take the time to cut a nice sharp corner at the base of the vertical wall.
• Next, measure halfway up from the Plant Shelf and cut a Rock Shelf into the wall 9” up from the bottom. That puts the Rock Shelf at 9” below water level. Carefully carve that shelf DEAD LEVEL around the entire pond, at least 6” wider than your rock coping, and wider still where you want to put Perimeter Bogs in behind the coping stones.
Don’t Forget the Bog Filtration
Finally, remember those Perimeter Bogs I keep mentioning? They’re a great natural way to help keep the water free of algae, by installing plants to consume nitrates that would otherwise feed algae blooms. They’re easy to construct anywhere there’s enough space to accommodate gravel behind the coping and still leave enough liner to pull up higher than water level. Add 10” of gravel to just above water level and plant with marginals, leaving only the soil they’re potted in, and they’ll soon start pulling nitrates out of the water, starving out algae. With rounded pond shapes there will usually be plenty of extra liner in the corners for bogs.
While pond building for lower maintenance can be as basic as the right Pond Kit and the right profile, here are some advanced tips on how to build a pond to save you even more work down the line.
Conduits in the Coping
Install some pieces of scrap pipe in the coping so one end opens into the pond under the stones and the other exits behind the rocks above the liner. You’ll be able to install the cords for pond lighting or the tubing for pond aeration through the coping, invisibly, never showing exposed and unattractive cords and tubing top of the coping.
Pond lighting should be part of your design from the beginning. Consider a light pointing up under the pond waterfall to light the waterfall from within, and silhouette lighting under pond waterlilies for an enchanting effect.
Pond aeration is a great idea summer and winter. Placed on the bottom when the water is warm, aerators promote great circulation and oxygenation. For pond winterization, the aerator should be removed from the deepest, warmest water and set shallow to keep a hole clear in the ice for gas exchange.
Active Bog Filtration
Supercharge your perimeter bogs by installing perforated pipes in the bogs before filling with gravel, then tee off some of the flow from the pump into the perforated pipe to deliver nitrates in the water column directly to plant roots.
If you’re considering a large pond and you have a spot that’s both close enough and lower than the bottom of the pond, investigate installing in a bottom drain to easily flush out debris without ever needing to drain the pond. Add a soil partition to the bottom to create two ‘Ponds within a Pond’, so a leaky valve will never endanger your fish. The pockets also provide a place for fish and plants so they don’t need to be removed if the pond ever needs draining for service.