Algae Control & Ultraviolet Lights
As you may know, an ultraviolet sterilizer is one of the best ways to guarantee clear water when the clarity problem is due to single cell algae making the pond water green. A UV will not help with filamentous algae. So why would a pond that has a UV still be green? If you are having this problem, it should be easily fixed. Below are the possible reasons for the problem.
First Step
First look and make sure the lamp is glowing. Your UV should have a clear portion or some type of indicator that allows you to see if the light is burning. You should never look directly at a glowing UV lamp as it can cause eye damage. If the lamp is not glowing then lamp is bad, the ballast is bad, or there is an electrical problem.
Improperly Sized UV Unit
Each ultraviolet sterilizer has a rating provided by the manufacturer for the pond size it will handle and the maximum flow rate it can handle. If your pump pushes more water than the unit will handle, the water flows too quickly, not allowing enough time for the UV to kill the algae. If your pond is larger than the UV is rated for then it will usually still provide benefit in killing algae but not to the degree you usually want.
Expired Lamp
Ultraviolet lamps don’t last forever. The life of a lamp depends on the manufacturer. Most UV lamps are good for 12-14 months of use. After this time, the lamp may still be effective but the amount of ultraviolet light output is significantly less.
Just because a UV lamp is glowing does not mean it is working, a lamp can continue to glow and still not be effective. It is best to track how long the lamp has been in operation so you can replace it for continued clarity.
Bad Ballast
If the lamp is not burning and it is not an old lamp, then your ballast (transformer) may be bad. You should consider replacing it. A ballast can go bad due to being flooded, lightning, or other causes of power surges.
Dirty Sleeve
The sleeve that protects the lamp from the water occasionally will need to be cleaned. It may get a build-up of deposits on it that prevents the UV rays from accessing the water. On most ultraviolet sterilizers this sleeve is made of quartz because it allows more UV light to pass through it than does glass. As such it is one of the more expensive parts of the unit, so be very careful not to break it (Never put a broken sleeve back into the unit as this could also ruin the ballast and lamp.) Simply cleaning this sleeve can make a big difference in pond clarity.
Dirt can simply be wiped off with a paper towel. If the sleeve is getting a white film then this could be a mineral deposit. Using a mild acid like vinegar or diluted muriatic acid will clean this.
Poor Placement of Pond Equipment
This last potential problem is one of the most overlooked aspects of pond health and clarity. The intake of your pump should be as far away as possible from where the water returns to the pond. If using a submersible pump then it should be in the water on the opposite end from the water feature, if using an external pump then the water pickup should be on the end away from the water feature. If your pump intake is right by the waterfall then the rest of the water in the pond is not regularly being circulated, filtered, or sent through the ultraviolet sterilizer.
An ultraviolet sterilizer is not a necessity in a pond, but one of the most popular luxuries. While pond clarity can be accomplished with excellent biological filtration and proper plant populations, a UV is the best way to guarantee water clarity. An ultraviolet sterilizer is NOT a replacement for biological filtration. A UV only makes the water clear, it does not help the general water quality. A properly balanced pond with good filtration is the only way to help your overall pond health.