About this time of year I begin getting calls regarding how to control algae growth in stock tanks. Algae growth is a fact of summer for livestock water tanks in Eastern Colorado. Before talking about controlling it, let’s talk about trying to limit some of the algae growth.
There are some basic essentials that algae require to grow in a stock tank. The most obvious is water and we can’t do much about that. Next, warm temperatures and sunlight dramatically promote algae growth. Some producers will build shade over their stock tanks to help with this issue. However, that creates an added expense and may cause problems with livestock trying to utilize that shade on hot days. Finally, algae needs some form of nutrients to sustain itself. This can come from livestock slobbers, animals urinating or defecating in a tank, and debris being blown into the tank. Part of this is unpreventable, but fencing or rails can be utilized to prevent livestock from entering a stock tank and introducing nutrients. If using rails, make certain they are positioned low enough that a cow can’t slip underneath the rail.
Once you have an algae problem in your stock tank, there are some treatment methods that you can utilize. There are numerous commercial products on the market. However, a generic approach to chemical treatment is often times cheaper. (Remember that chemical treatments may change the taste of the water for a period of time. Also, these need to be mixed thoroughly within the tank for a few minutes before livestock are allowed access. Don’t just dump it in one part of the tank and drive off.)
Chlorine Bleach: Sodium hypochlorite (5.25%), which is what many of the standard laundry bleaches (only use unscented) are made of, can be effective. You will need to add 2 to 3 ounces of the 5.25% sodium hypochlorite for each 100 gallons of tank capacity. Be sure to mix the tank water well after adding the bleach. This should be repeatedly weekly. When temperatures are abnormally hot and when a lot of organic material exists in the tank, the sodium hypochlorite will dissipate more rapidly and may require multiple treatments per week.
Copper Sulfate: Copper sulfate is a popular algae control and is found in many of the commercial products. It will often come in a crystal form and needs to be dissolved in warm to hot water before making the treatment. Typically, 1.5 teaspoons should be dissolved in 4.5 ounces of water for each 1000 gallons of tank capacity that will be treated. This mixture is then poured throughout the tank. Treatment should be repeated in two to four weeks, depending on algae growth. Algae killed using this method should be removed from the tank and hauled out of the grazing area, as it may contain very high copper & sulfur levels. The use of copper sulfate is not recommended when sheep will be consuming the water, as sheep have a low tolerance for copper and this treatment may be toxic to more copper sensitive sheep. Another important note is that copper sulfate can increase the rate of deterioration of metal tanks and pipes.
Zinc Sulfate: Zinc sulfate is another chemical treatment. Again, the material needs to be dissolved in warm to hot water before being added to the tank. In the case of zinc sulfate, dissolve one cup in one gallon of water. Then thoroughly mix into the tank ½ cup of the solution for every 100 gallons of tank capacity. Repeat as needed.
Biological Control: In these times of consumer concerns over what is in their meat, more and more producers are turning to herbivore consuming aquatic life to maintain reduced algae levels in stock tanks, as opposed to chemical treatments. One of the more common resources is the goldfish. It will take 4 to 6 goldfish for every 100 gallons of tank capacity. Other aquarium species can be more expensive ($3 to $6 each) but still effective. Some of these are the Black Mollies, Otocinclus Catfish, and my personal favorite the plecostomus. Some varieties of plecos, like the Trinidad Pleco, can grow to near a foot in length and spend a surprising amount of their time foraging.
While these biological control techniques do offer a good marketing statement for those selling in all natural programs, they still create issues. First, you are trading algae for fish feces in your tank. Secondly, fishing predators (raccoons, cats, birds, etc.) may become attracted to your stock tank & treatment technique. Thirdly, if you are changing pastures throughout the grazing season you will need to move the fish. Finally, you will need to have a plan for caring for the fish during the winter months.