Hazes and Greenwater in Koi Ponds

Sometimes the source-water used to fill a facility or pond will have a lot of minerals, sediments and other dissolved solids in it. This is not uncommon with rural wells. This water should, most ideally, be passed through a water purifier before use. There are quite a few of these water purifiers on the market, including a "reverse osmosis" unit which uses a series of extremely thin membranes to remove solids from the water. Reverse osmosis can make crystal clear water out of most any fluid source. I have seen one unit which uses reverse osmosis and the manufacturer pours a Coca Cola in one end and gets water out of the other. Reverse osmosis is an expensive concept. Other ways to refine water of suspended mineral solids is to lagoon the water with abundant vegetation, or even in a plain vat to allow such solids to settle. Certain flocculants such as API's AccuClear can be used for this purpose as well.

 The final cause of water hazing which needs to be discussed is the overgrowth of suspended green algae, also known as "greenwater". The algal bloom can be "minor" permitting the fish to be viewed through a pale green haze, or it may be severe, obscuring your view of all objects below the surface. Green algal blooms (greenwater) is usually entirely harmless to fish. In fact, the Japanese, and many American ornamental fish growers believe that green water is the healthiest water to rear fish in.

 Fisheries biologists will not even try to rear baby fish in anything but green water because the microalgae form an important food source for new fish.

 One important practical consideration of green water is that during the day, the suspended algae will produce prodigious amounts of dissolved oxygen through a process called "photosynthesis". At night, the algae cease to contribute oxygen through photosynthesis and they begin their respiration-phase. In this phase, they utilize nutrients and energy to grow and in this phase they USE oxygen and produce carbon dioxide. Knowing this, it is easy to see how in darkness, the suspended green algae can be as dangerous as it was helpful in broad daylight.

 The best way to curb algae which might contribute to a green haze or pea-soup looking water is via "ultraviolet sterilization". At first, the units might seem expensive, but that's very relative. If you buy your UV without price shopping the different brands, you will pay too much. Look around and try to see past the marketing hype. Try to find a UV with durable construction and the very first question to ask is about replacement parts. You need to "see" the replacement parts. Do not settle for the lame assertion that "They are available" because I assure you that they are usually not. You should only buy from a dealer and a manufacturer with the economic clout to have and stock spare parts.

 The investment in a UV is a good one because it will clear two out of three of the above hazes. The UV can kill bacteria and algae that might cause hazing. You should replace the bulb as soon as it seems to be failing your pond. You may still see a blue light emitted by the bulb but it won't be emitting a true UV radiation after a time. Normally, the bulb's failure occurs after twelve to fifteen months. It's reasonable to hope to get two full summer-seasons out of a bulb. This is why replacement bulbs are nceessary. Hard-to-get parts make the owenrship of a UV into a nightmare.