Keep Biofilm Out of Your Flock’s Drinking Water

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Poultry drinkers that aren’t regularly scrubbed often develop bad-tasting biofilm that discourages drinking. Reduced drinking, especially during hot weather, can lead to dehydration, poor health, and fewer eggs.

Biofilm is a fancy word for the thin layer of smelly scum that can develop in drinkers and water lines. The two most common kinds of biofilm in poultry drinkers are caused by algae and iron. If the scum is green, it’s caused by algae. If it’s rust-colored, it’s caused by iron. Algae biofilm is more common, but iron biofilm can be more hazardous to your flocks’ health.

Maintaining clean water for your flock will play a large part in keeping them healthy and happy.
Maintaining clean water for your flock will play a large part in keeping them healthy and happy.

Algae Biofilm

Green algae biofilm itself isn’t harmful; in fact, some chicken keepers believe it’s beneficial because it filters the water by removing organic waste matter. But the presence of algae indicates that the water is polluted with the type of nutrients algae thrive on. And if the biofilm is left long enough for the algae to start dying, they’ll release pollutants back into the water. Living or dead, algae can impart an odor and flavor to the water that your birds may not like, and anything that discourages drinking is unhealthful to the flock.

Green algae need four things to grow: water, nutrients (fertilizer), light (for photosynthesis) and heat. Because algae are heat-loving, algae biofilm in drinkers is a greater problem in summer than in the cooler months of winter.

Algae are likeliest to grow in glass or plastic drinkers because glass and plastic let in light. Galvanized drinkers, on the other hand, block light and algae can’t grow in the dark.

Minimizing the amount of light that falls on glass or plastic drinkers helps control algae. Outdoor drinkers should be kept in the shade. Even indoor drinkers will develop algae if the coop lights are on more than eight hours a day. Wrapping a drinker in a jacket that blocks out light is cumbersome, but does discourage algal growth. Using galvanized drinkers resolves the light issue.

Nutrients may be furnished by your birds or may already be in your water supply. If you are battling algae biofilm in your drinkers, the first thing to do is examine your water. Although the chlorine in municipal tap water should discourage algae, you can find out what else is in your water by obtaining a water quality report from the office of your local water district. If you have a well, have the water tested, particularly for phosphorus and nitrogen — the two nutrients algae like best.

Poultry may furnish nutrients by scratching litter into the drinker, pooping in the water, or dropping feed from their bills or beaks into the water. Using nipple drinkers prevents these issues. Hanging bell waterers, or placing them on platforms with the trough part about the height of the chickens’ backs, reduces the chances of nutrients getting into the water from scratching or pooping. Putting some distance between feeders and drinkers reduces the amount of feed that gets dropped into the water. Ducks and geese are especially likely to get feed into their water unless the feeder and drinker are at least six feet apart.

Copper is toxic to algae, so putting a piece of scrap copper plumbing or a few copper-plated zinc pennies into the drinker is another way to discourage algae. Since algae prefer a low oxygen environment, the ideal way to control it is to avoid letting the water get stagnant by frequently emptying and scrubbing drinkers, and refilling them with fresh water.

Of the many species of algae, some are indifferent to the water’s pH, some prefer a low pH (acidic water), and some prefer a high pH (alkaline water). Most species, however, don’t do well in acidified water with a pH less than 5.5.

Iron Biofilm

Iron biofilm needs three things to grow: a low-flow water supply, a rough surface, and dissolved iron. This biofilm grows best at a temperature range between 40°F and 75°F, but can tolerate temperatures as low as freezing and as high as 107°F. It is not affected by light one way or the other, and can grow in complete darkness. In the poultry yard it is most likely to be found in dark places where drinking water is relatively undisturbed — coating the insides of reduced-pressure water pipes leading to automatic drinkers and the inside surfaces of galvanized metal bell drinkers.

Iron biofilm develops in a metal drinker where the water has a high mineral content. Photo by Gail Damerow
Iron biofilm develops in a metal drinker where the water has a high mineral content. Photo by Gail Damerow

Since the chlorine in tap water helps control it to some extent, iron biofilm is associated with well water that has a high mineral content. It starts as a flaky deposit, called scale, caused by the minerals in hard water. Hard scale is crusty and results from iron and manganese. Soft scale is light and spongy, therefore easier to remove, and is caused by calcium and magnesium. You can tell your water is high in mineral content if it leaves yellow or rust-colored stains around drains or discolors laundered white clothing. Such water also tends to have an unpleasant metallic taste.

Scale accumulates more rapidly on the rough surfaces of copper plumbing and galvanized drinkers than on the smooth surfaces of PVC plumbing and plastic drinkers. Its presence increases the roughness of the surface, creating pits that give silt and other fine particles in the water a place to stick and that provide microbes in the water a place to hide.

Among the first microbes to take advantage of this environment are iron bacteria, which take advantage of scale to grow into an active colony through cell division and by recruiting other iron bacteria. The bacteria produce a gelatinous slime that both protects the growing colony and traps more silt and other sediment, which provides additional protection.

Iron bacteria don’t cause disease. Their chief claim to fame is their ability to absorb and accumulate dissolved iron, and sometimes manganese, from water. They live and reproduce by deriving energy from iron and manganese, and they deposit iron and manganese salts around their cells. The resulting rust-red slime has an unpleasant swampy-rot odor and makes the water taste bad. Barnyard poultry don’t like bad-tasting water, and hens that don’t get enough to drink don’t lay well. Chunks of biofilm that break away inside a water line can clog automatic drinkers, causing them to leak or fail altogether.

A greater problem can occur if the iron bacteria colony attracts other microbes that otherwise wouldn’t stick to plumbing and drinker walls, but that take advantage of the protective environment created by the iron bacteria. These moochers may include such pathogenic bacteria as campylobacter, clostridia, E. coli, listeria, salmonella, and staphylococci that can spread serious diseases through your flock. Outbreaks of botulism in broiler flocks have been associated with iron-rich drinking water.

Organic matter — especially sugar, vitamins, and some medications added to drinking water — clings to the slime and provides its inhabitants with nutrients. Left undisturbed, a colony can grow pretty fast. In a matter of weeks, it can reduce the inside diameter of a 6-inch water pipe down to two inches. Even inside a frequently refilled bell drinker, a colony can develop rapidly if the inside drinker wall is not regularly scrubbed.

Chlorine and other disinfectants have no effect on bacteria embedded in biofilm. The slime must be removed before a disinfectant has any effect. Flushing water pipes with pressure, where feasible, and scrubbing the inside walls of drinkers at least once a week will control iron biofilm. In warmer weather, which encourages a rapid increase of pathogenic microbes, daily scrubbing may be necessary.

Aside from treating your well, which is best left to a professional, you can reduce the development of iron biofilm by installing a water filter. The most common filter for home use is 10-inch by 2 1/2-inch diameter filtration unit that takes a relatively inexpensive pleated, cord-wound, or polyspun filter. Pleated filters come in paper or polyester. Paper is slightly cheaper, but polyester lasts a little longer. Cord-wound filters and polyspun filters last longer yet. Any of these filters will remove dirt and sediment, including iron, but not bacteria or other microorganisms that might be in the water.

Water filters are rated in microns, a metric measurement equivalent to one-millionth of a meter. The micron rating indicates the ability of the filter to remove contaminants by the size of its particles. Most water filters are in the 5- to 25-micron range. To offer a point of comparison, the diameter of human hair ranges from 40 to 90 microns. The lower the micron rating, the finer the filtration. The finer the filtration, the more rapidly the filter will clog up. At best, any new filter is only about 60 percent efficient and becomes more efficient as it traps more sediment, but the accumulating sediment gradually reduces water pressure to the point that the filter must be replaced to restore adequate pressure.

Scale forms faster in water with a pH higher than 7.0. Below 7.0, minerals tend to settle out as sludge. Iron bacteria prefer a pH range of around 6.5, but can get along in the 5.5 to 8.2 range. An acidifier that reduces the water’s pH below 5.5 can therefore help discourage the development of scale and iron biofilm. An acidifier cannot, however, penetrate and remove an existing biofilm.

Controlling Biofilm

Because algae biofilm and iron biofilm are both discouraged by a low water pH, adding one tablespoon of vinegar to each gallon of drinking water (double the amount of vinegar if you have hard water) helps control both types of biofilm. On the other hand, putting vinegar in a galvanized drinker can cause the water the develop a metallic flavor your birds might not like, and the vinegar will hasten rusting in seams, scratches, and other spots that are not adequately protected by the drinkers’ galvanized coating.

This water shows the beginnings of algae biofilm that can develop in glass or plastic drinkers exposed to light. Photo by Gail Damerow
This water shows the beginnings of algae biofilm that can develop in glass or plastic drinkers exposed to light. Photo by Gail Damerow

Gail Damerow is the author of The Chicken Health Handbook, The Chicken Encyclopedia, Your Chickens, The Backyard Homestead Guide to Raising Farm Animals, Hatching & Brooding Your Own Chicks, and the classic Storey’s Guide to Raising Chickens. Gail’s books are available from our bookstore.

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