turns ammonia into nitrate which is harmless to fish (unless at
extremely high levels) but the disadvantage of this is that algae love
nitrate and you get an algae bloom. There are two types of algae
problems, green water and blanket weed.
Green water is caused by microscopic algae in the water, it is not
harmful to Koi, actually it is beneficial, the Koi eat the algae and it
enhances their color, but you can't see them!
|Also in summer the algae use oxygen and
leave the fish gasping. There are various ways to get rid of the algae,
probably one of the most widely accepted is an ultra violet (UV) filter
which kills the algae as it passes through.
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 filter, 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?
Purely for green water eradication, 8-10 watts per 1,000 gallons is
usually recommended, but some pond keepers will maintain that, for a
reduction of bacterial levels, this can be increased threefold to 30
watts. Other factors to consider are of course flow rates, and stoking