This is peak season for pond owners and garden pond builders. All the plants are blooming and the fish are very active. Our fish will come to the top of the pond when someone is around in anticipation of being fed. My son loves to feed the fish every morning when we get to the office. My other son says, "fish" every time we are close to the door or outside. We have a very pretty pond and waterfall here at the office that is very low maintenance. We are blessed with a good balance in the pond and the water stays clear. Unfortunately we are in the minority because most people call us this time of year begging for help with their Green Water.
Green water ("PEA SOUP") is caused by suspended algae in the water. The sunlight blooms this microscopic algae along with all the other plants in you pond. This algae also feeds off of waste products produced by the fish. The more fish you have the more likely you will have an algae problem. So what to do about this one will ask.
If you want to solve the problem and not keep treating it then a ultraviolet light is the way to go. The problem a lot of people face when choosing a UV is the want the cheapest unit they can find instead of properly sizing a correct size unit out for their application. There are a few things we like to know before suggesting a size. #1 how big is your pond and the second question we always ask is what size pump are you running. Obviously if you choose a small unit for a large pond it will not work. Also when considering your pump there are a few things to keep in mind. If you use a small UV unit with a large pump pressure you risk the chance of blowing the seals on the unit thus rendering it useless and voiding the warranty. Also if you run the water thru it too fast you will not get the clarification you need. Most UV units have 2 rates of flow. A clarification rate and a sterilization rate. For clarification the rate is usually a faster than for sterilization. The water needs to be slowly passed by the light in order for it to disrupt the life cycle of the blooming algae in the water.
Another thing to consider with maintenance of a UV light is to regularly change your bulb. It is recommend to change your bulb once a year, usually at the start of season. Sometimes it may still be burning but it will lose it effectivity. When using a UV, also remember if you add bacteria or other treatments you need to shut down the UV for 18 hours after in order to let the treatments work or bacteria to thrive. The light can also disrupt these treatments just like it disrupts algae.