Algae Control - No more green water
UV-Clarifiers kill 99% of single cell floating algae (green water) as well as a small percentage of disease organisms. They do not harm the beneficial bacteria that grow in filters and on rocks, etc. in the pond. They only kill the organisms that pass through the UV.
How does a UV Filter clear green water?
Single-celled green algae, (Chlorella vulgaris) require light and nutrients to thrive. It is one sign that your pond is generally healthy, and it even makes a great food additive for farm animals, but it doesn't do much for your overall enjoyment of viewing Koi!
The small algae cells can pass through all conventional filters, so physically filtering them out in their normal form is next to impossible. However, passing the cells through a UV disrupts their internal structure, if not actually killing them, at which time they clump together or 'flocculate'. These clumps can then be trapped and broken down by the filter.
When to use a UV:
Most Koi keepers will keep their unit(s) on year round. But for small garden ponds you may find that only in the spring, with the combination of longer days and an upsurge in fish activity, is UV necessary. If you do run your UV year-round, it must be protected from frost in a well-ventilated housing. Remember it is important to replace your UV lamps annually for peak performance.
How much UV do you need for your pond?
For green water eradication, 8-10 watts per 1,000 gallons is usually recommended. However, to properly size your UV you must consider your pond gallons, the filter size, the amount of sunshine per day and the fish load. A very sunny pond with a lot of koi and a small filter will need more UV power to give clarity. You may consider to up size your UV in order to give the best results for your situation.
It is possible to kill some harmful bacteria by passing the water very slowly through the UV but in general it is only practical if your UV unit is very large. Some pond keepers will maintain that, for a reduction of bacterial levels, the wattage size of the UV can be increased threefold to 30 watts per 1000 gallons.
What is the correct flow rate through the UV ? Every UV unit has a suggested maximum flow rate listed in the literature or on the unit itself. While there is a considerable safety factor in regards to flow rate you should try to reach the maximum flow for the unit. This will ensure you are getting the most efficient use of the unit size. Another very important consideration is the pond gallons in relation to the flow rate through the UV. The goal is to pass the pond volume through the UV a minimum of one time every two hours. This is 12 pond turnovers per day. A slower turnover than this will allow the algae to grow faster than the UV can kill it. You will get better results when you pass the pond volume through the UV one time every hour. However, check the recommended flow rate on your unit and try not exceed it.
My brother, Colton Cooke, and I standing next to our Mega UV that we run on the Play It Koi show pond! (Don't worry, Most UV lights Systems for backyard Koi bonds are not nearly this large)