Water Changes

By Graham Hawkins

Abstract:

Water changes occur naturally in nature. Stocking densities are lower in nature. By contrast, in your pond, “new” water has to be added by you. New water” is important in closed systems because it dilutes nitrogen, proteins, gases, and replaces important compounds like trace minerals and carbonates. Your pond may be a “natural ecosystem” but it your fish require periodic water changes, [unless your pond has got a stream or creek running into it like Mother Nature has engineered for her ponds and lakes.]

Pond experts do not universally agree upon the subject of “water changes”. May people do water changes differently, some do not do water changes at all. This article attempts to explain why water changes may be quite important in smaller, closed ecosystems (The ponds) kept by hobbyists.

Understand Nature

In nature, lakes and ponds are usually massive bodies of water. This is especially true on a relative level, when compared to the life within them. Natural bodies of water get massive, regular water changes…they are open systems, most being spring/brook/river fed. Natural bodies of water are generally stable environments, where very little ever changes…mind you this is changing, due to acid rain. Where acid rain is a problem, fish and amphibian populations are being adversely affected by deteriorating water conditions. The physiology of our fish is designed for stable environments.

Understand Your Pond

In contrast to large, natural bodies of water, our ponds or aquariums are much smaller, closed systems. Therefore all the chemical elements within them are getting concentrated on a daily basis. The same type of thing happens when water evaporates…elements get concentrated. Continual “topping up” of a pond will just allow the water to get more concentrated, and harder (GH levels) while any toxins present in the water also become concentrated. Conversely, in closed systems over time, other desirable elements get depleted by natural biological processes occurring within the pond.

So to restate, in naturally occurring ponds and lakes there are low densities of fish, coupled with high replacement of “new” water.

In closed systems, like in a pond, there is limited inflow of “new” water and the ecosystem tends to be crowded.

Carbonates

Carbonates are basically chemicals, which dissolve in water to support the pH, or prevent the PH from becoming too “acid”

Over time, the natural trend for carbonates is “exhaustion” or the process of being used up. Sooner or later, carbonates must re-enter a system or the pH cannot be supported. When the pH falls too low, the biology (life) in the system is ended.

Depending on the source water for the closed, hobbyist pond, and the amounts of acid rain falling, one of the first things to get used up is the waters buffering ability, the KH, carbonate hardness. Without this element being maintained (naturally or artificially ) in the 80 ppm* range, it's possible for the pH to crash…that is to drop to extreme levels, with the potential to kill your fish. Depending on the aggregate or stone chosen, the rock and gravel in an AS system, along with water changes may maintain it. Fortunately, the carbonate (alkalinity) levels are easily checked and adjusted with a simple test kit.

The moment that we add anything which lives and respires to a body of water it starts to use elements from that water and put other elements back. Of importance in this are the nitrogen compounds, Phosphates and Carbon Dioxide. They’re pretty easy to understand.

Nitrogen

In our pond, our fish give off a waste product called ammonia, which gets oxidized through a series of natural steps, to nitrate, which can build up in undesirable ways… Rural farming areas [where fertilizers are used abundantly] may have nitrates in their water supplies that'll add to these levels. Fortunately for us, plants in the pond will use Nitrates, but they can only use so much. An excess of nitrates hurts the fish and causes green water.

Phosphates

Our tapwater supplies, plus applied fertilizers and fish foods all contain phosphates, which will build up given time. Some local water companies are adding phosphates to cut down on “scale” within their pipes, unfortunately we end up with algae from the phosphates. So you see how nitrogen and phosphates can “gang up” to cause algae problems.

When you engage in water changes, you reduce these nitrogen and phosphate accumulations. The net effect is beneficial to the fish.

Biologically Active Proteins

The fish also give off hormones and pheromones…ever wonder why one fish will grow like crazy and the others stay small?… it’s growth inhibiting pheromones.

Dissolved Organics

Pheromones are just one of the elements that make up “dissolved organic compounds” or DOC’s - Other elements that can contribute to it are fish mucus, bacteria, undigested fats, carbohydrates, amino acids …anything that is part of the life processes of the pond. Have you ever seen that foam that forms at the waters edge at the beach, or at the base of a waterfall or that oily film that occasionally forms on the surface of a pond or an aquarium?…That's basically DOC, so you’ve seen it in real life. T here are studies that show fish raised in high “dissolved organic compounds” water have slower growth, lower disease resistance and lousy colour and form.

Then there are trace elements and minerals that we can't even measure with our pond type test kits that are used on a continual basis. These trace elements are important to fish metabolism and are replaced by “new water”. Without “new water” the fish suffer.

Here are just some other areas where water changes help:

Replacing Carbonates:

The pH-supporting Carbonates are continually used up by the nitrification cycle. It turns out, lots of hydrogen is released from Ammonia in its reduction. These hydrogen molecules would hazardously reduce the PH of the pond if carbonates didn’t stop it.

Carbonates are also used up as they buffer the pH at night. This is because at night, plants use oxygen and give off carbon dioxide, which forms carbonic acid. Carbonic acid drags down the PH unless our friends, the carbonates are there to stop it.

All these compounds and by-products have to be removed, diluted or replaced to maintain healthy water quality. Water changes accomplish all these goals. Sometimes, part of this can be done with bacterial additives, trace element additives, continual low dose PP (potassium permanganate) treatments… All that sounds kind of tricky. We should consider something as simple, safe and affordable, as a 10% to 15% weekly water change.

Or, if you’re not into weekly pond care, spread the water changes out by making larger changes (20%-30%) every 2-3 weeks.

As you can see from the above discussion, keeping more fish, and the increase in metabolism in the pond results in greater pressure on the environment and an increased need for water changes.

Water changes are a “must” for real success with pond fish in your water feature. Small regular water changes are the way to go. These can be done in conjunction with regular maintenance, such as cleaning the skimmer mats, or vacuuming out excess crud.

Can you Change Too Much Water?

Yes. The larger the water change, the greater the stress put on the fish. …This is because we cannot match temperature, pH and other water-quality elements [in huge water changes] closely enough not to stress the fish…Please keep in mind,

Stress => Vulnerable immune system => Possible disease.

Graham Hawkins © Jun/2/04