Spring startup is a term irrigation contractors are familiar with. In the pond market, we call it ‘spring cleaning.’ Before the season cranks up, over the winter months it’s always good to review what happened and refresh your thinking. Here are a few sometimes-overlooked points that we need to pay attention to.


It’s a good idea to clean up the water lilies and put time-release fertilizer tablets into the containers, if they’re in them. If they’re planted loose in the gravel in the bottom of the pond, tuck a couple of tablets around each major root mass, to give them an extra boost. They’ll bloom better with that extra helping hand.

Plants around the edge, or in shallow water, need to be thinned out periodically. Familiarize yourself with the pond plants commonly used in your area, especially any species that are on the aggressive side. If you find yourself ripping out a half or three-quarters of a certain plant every year, you may want to replace it with something else.


If the pond has fish, I don’t recommend moving them unless you absolutely have to when water temperatures are less than 50 degrees. However, if you have to move them, before you take the fish out and put them in your holding tank, be very careful what type of net you use. Widely spaced netting can injure fish.

If the fish are eight to ten inches long, a sock net (a long tube, about three-and-a-half feet long, with an opening on the bottom) is recommended. With heavier fish, their own body weight is their worst enemy. Some contractors who deal with high-dollar koi won’t use nets at all; they use plastic bags with one corner nipped off so they can adjust the water level.

Always put a lid on your tanks. If you forgot the lid, don’t fill your temporary tank more than halfway full. It makes it harder for the fish to jump out.

If you’re dealing with a large number of fish—or large fish—use a supplemental air stone in the tank.

Keep an eye, and a nose, on that tank. If the water starts to smell ‘fishy,’ change the water immediately! That smell is caused by ammonia. Fish emit higher amounts of ammonia when they’re under stress or running out of oxygen. At that point, it may be too late to throw in an air stone.

Some ponds that contain fish don’t require full cleanouts. Ponds with bottom drains, or those that have debris filters that get flushed externally, are in that category. But fish-filled ponds or features with total rock and gravel on the bottom must be periodically drained, and the muck removed from the bottom. It should be done at least once a year; the health of those fish depends on it.

If this muck-out isn’t done, the debris buildup will eventually cause the pond to go septic, or anaerobic. A pond that’s even partially anaerobic will start emitting sulfur hydroxide. Even in very minute amounts, it’s lethal to fish. An annual cleanout is an insurance policy against that.

Some people in Northern climes leave their fish in their ponds over the winter. That’s fine, as long as there is an opening somewhere in the ice. There should be something, whether it’s a heater that just melts a little circle on top of the pond, or an extra pump that pushes up a little geyser through the ice, so that gases can exchange.

If a pond owner tells you his fish died over the winter, lack of an opening is probably why. Even a frozenover pond still has bacteria in it, busy bio-converting organics and using oxygen. With no opening, toxins build up from those processes; the oxygen level drops, and the fish die.


Be responsible about where you’re dumping the old water. In some areas of the country now, it’s illegal to put pond water down a storm drain, as it’s classified as graywater. Most people have neighbors, so make sure you don’t create a Grand Canyon in someone’s flower bed.

Double-check where that dirty pond water is going to go, or you may drain it right into somebody’s spa or swimming pool. Then you’ll be liable for whatever the pool guy wants to charge to get that stuff out.

When you clean a pond, there’s going to be a considerable amount of black gunk at the end of your cleanout pipe. Don’t just dispose of that any old place; spread it out in a mulched area where it won’t be an eyesore. That black gunk is good for plants, as it is essentially fertilizer.


Checking a liner for holes is usually a waste of time, initially. The most commonly used liner in residential, ornamental waterscapes or water features is 45-mil EPDM rubber liner, a material with an excellent track record. The only leaks I ever see in rubber liners below the water level are usually after a windstorm has come through, and a branch fell out of a tree and punched through it.

In most of the U.S., pond and water features run 24/7, 365 days a year. If there’s a problem with a liner, someone’s going to notice it right away. The first indication of a liner leak is loss of water. If it’s not losing water, there’s no need to look for a leak.

When a client calls with a leak issue, check out the attachment points and make sure electrolysis—from using fasteners with two different kinds of metal—is not the culprit. If they need to be replaced, drill them out and put in new, all-stainless-steel screws and bolts with flat washers on each side, and locknuts so they don’t come loose. I usually renew the silicone seal as well.

If it’s not a hardware issue, it’s possible that the original installer cut the liner too short. When the pond was built, fresh dirt was in place, the liner was an inch above the water level and, possibly, the contractor didn’t compact it very well. Over time, the dirt settled and now the liner is lower than the water level.


Some pond guys wash down their ponds and water features with pressure washers, to give their clients that ‘brand-new’ look. From a biological standpoint that’s not a good idea. It has taken that pond a year, or several years, to become biologically balanced, or ‘seasoned.’ When you pressure-wash all that biofilm off, yes, you’ve made it look new again, but you’ve also set back the process that keeps the pond balanced.

Instead of pressure washers, I use volume pumps. These pump a volume of water to rinse out the nooks and crannies, but won’t blast off that biofilm.

Pumps and skimmers

Many pond and water feature owners do their own skimmer cleanouts. Some are more conscientious than others. If you’re not doing the monthly or bimonthly service, spring cleaning time gives you a chance to check and see if the owner missed the horned toad that got into his skimmer leaf net or basket and ripped a fist-sized hole in it, or if there are any other cracks, breaks, or holes. If there are, you’ll need to order a replacement.

Holes in a skimmer leaf net or basket can be disastrous for a pump. If leaves or debris are able to escape the skimmer, they’ll be pulled directly into the pump.

Some pumps should be checked once a year, depending on what kind you’re using. Most of today’s modern submersible pumps aren’t really designed to be taken apart and serviced, other than those with pre-filters.

Cheaper pumps have pre-filters on them. These should definitely be pulled out and cleaned at least once a year as part of a spring cleaning. A shop vacuum works well for the skimmers. Do the same thing with the waterfall filter boxes and filter mats.

Pumps with fairly fine pre-filters are going to get clogged. Clogging up the intake side of a submersible pump is not good for the pump because you’re starving the pump of water, and it is designed to run under load.

It’s just like the motor on your car.

If you put your car in neutral, and press on the accelerator as if you’re going 70 mph on the interstate, it’ll over-rev, burn up and die. You’re running the engine without going anywhere, and without any wind and gravity resistance.

You can restrict a pump, however, on the discharge side. If there’s too much water going over the waterfall, you can turn it down 15 to 30 percent. That doesn’t hurt the pump, because it’s still under load. In fact, a lot of pumps like some resistance on the discharge side. They’ll perform better, and may even last longer.

Remember that the system is running with dirty water. You may have gotten everything else spic and span, but don’t forget that you’ve still got dirty water in the pipe between the pump and the waterfall. Get clean water into the skimmer, fire up the pump, and push that dirty water out of the pipe up into the waterfall box. While you’re using that shop vacuum, suck up that dirty water, too.

That’s a little trick of the trade.

Dechlorinator and pH

When it’s time to refill the pond, remember that most of your clientele will be hooked up to municipal water with chlorine in it. To get the chlorine out, I use sodium thiosulfate in crystal form. Most liquid dechlorinators are just a diluted mix of those crystals dissolved in water. There are also some more expensive dechlorinators out there that use advanced chemistry, and they do have their place.

The problem with the liquid sodium thiosulfate is that it evaporates. Even with a decent lid on the container, the odds are that within a month or two, it’ll be gone. The crystals, on the other hand, have an almost infinite lifespan, as long as you keep them out of the sun and under 120 degrees. It only takes a level teaspoon per 100 gallons of water going in, so a pound of crystals will go a long way.

The pH is important. Soft water won’t hold a stable pH. When you’re doing a 100 percent water change, and you know the water is soft, you should add somewhere between a third- to a half-pound of baking soda per thousand gallons of new water. It helps stabilize it so the pH doesn’t radically swing and kill your fish. Everything else in the pond can handle pH swings, fish can’t.

A final note

These are a few of the things I’ve learned over the 20 years I’ve been working with ponds and water features. One of the most important things is that I’ll never know it all; I still learn new things all the time.

No professional should ever stop learning. Why do you think doctors keep reading medical journals throughout their careers? The owner of Aquascape, Greg Wittstock, once said, “You stop learning, you stop earning.” So keep learning and keep earning. I will.

EDITOR’S NOTE: Dave Jones is the owner of The Pond Professional.