By Staff
Must be pond algae is a widespread problem for last week's column on controlling algae generated a lot of response, not only from fellow Michiganders but places as distant as Bulgaria.
It appears I goofed by focusing on the commonly used chemicals to treat pond algae. Expressed interests are in more environmental friendly, non-chemical methods which I only briefly touched on so expansion is in order. As small garden pools and such are fairly easy to manage I'll aim mostly at larger natural or created ponds. If you'll recall, two types of algae cause the bulk of the problems. Plankton algae free float in the water and cause the pea soup appearance. String algae grow in long filaments then float to the top, forming the pond scum that looks like floating wool mats. Both thrive in stagnant water containing a lot of nutrients from decaying debris and other sources. Barley straw is in vogue but that and its inconsistent effectiveness was detailed last week so we'll move on.
Aerating the water is a very benign and pond healthy method of algae control. Nutrients are insoluble in oxygen rich water so they sink to the bottom where the sun loving algae that live higher in the water column can't get to them. There are a variety of aerating systems available from simple water circulators to fountains and underwater pipe systems. Which type to use depends on the size, depth and complexity of your pond. Most require an electricity source but there are wind driven models. The price tag for a standard, small pond size system starts at around $1000.
A company called BioWorld of California replied to the column suggesting introducing algae competing microbes. They supply kits that include microbes which out-compete the algae for the available nutrients, starving out the algae. You must get the right kit for the type of algae, string or plankton. It's an ongoing process throughout the growing season, treating heavily at first then reducing the amount and frequency of applications. There are a lot of variables in the amount required and ensuing cost but for here in the upper Midwest an annual cost of about $1200-$1300 per acre of pond is a guess. This biological attack is well suited for larger ponds where mechanical systems have difficulties. The microbes are reportedly completely safe and have no ill effect on the pond's ecosystem.
A system that has long been in use for aquarium and small garden pool algae control is ultraviolet sterilization. Ultraviolet light is the standard sterilizer for everything from medical tools to drinking water. This system pumps the water through a unit where it is exposed to ultraviolet light, killing everything. The debris is then picked up by a mechanical pond filter leaving the water crystal clear. In a pond scenario not all the water gets pumped through so the pond isn't a complete biological desert but it leans in that direction. Obviously, the pond's natural ecosystem is severely altered. This only works on free floating plankton algae, not string algae, and is best suited to quite small ponds.
An algae control method that has been in use in Europe for several years but just getting a foothold here in the U.S. is ultrasonic sound. You know how an opera singer can shatter a glass by hitting just the right note? These units work similarly by emitting sound vibrations at a frequency which break down the cell walls of the algae. It works on both plankton and string algae and is reportedly harmless to all other life forms. I don't know. I have to wonder if aquatic bugs and other creatures being constantly bombarded by weird vibrations don't get to feeling, well…buggy. Proponents of this system say no. The effective sound range depends on unit size and ranges from one hundred to six hundred feet. Multiple units can be used for larger or irregular shaped ponds. A garden pond unit runs about $1000 and a 1-2 acre pond model around $2400. I've surely overlooked some but these are viable alternatives to chemicals for algae control. Carpe diem.