Why are water changes so important?

Regular water changes are a very important part of raising healthy koi to their full
potential. The following are just a few of the reasons why regular water changes are so

- Regular water changes prevent the build up of anti-growth hormone in the pond. Koi,
like many other fish, are constantly giving off an anti-growth hormone which, if allowed
to build up in the pond water, will greatly reduce the ability of the koi to grow, no matter
how much food you give them. In general, koi tend to grow bigger in a large pond rather
than in a smaller one. This is more a factor of how much of this anti-growth hormone
has built up in the water rather than how large the pond is. A large pond having more
water and requiring more fresh water to clean it’s filter from time to time will usually have
a lower level of this hormone in it. In a smaller pond this hormone can build up very
quickly. Regular water changes will keep this anti-growth hormone from building up at
all, thereby allowing a koi to grow to its full size potential.

- Regular water changes can reduce the level of organics in the pond water. Organics
in the pond water can come from a number of different sources such as, koi waste,
excess food, decaying debris and a number of other sources. These organics can
become so small that they will travel right through the ponds filter and are often referred
to as Dissolved Organic Compounds or DOCs. Therefor, these DOCs can cause
the water to appear cloudy and can form on the water’s surface causing bubbles.
Additionally, these DOCs are a source of food for any bad bacteria in the pond. Regular
water changes can greatly reduce the level of bad bacteria in the pond water, thereby,
reducing the chances of your koi getting sick due to a bacterial infection.

- Regular water changes will help reduce the build up of nitrates in the pond water.
The biological filter on a pond converts the ammonia produced by the fish to nitrites
and eventually to nitrates. Nitrates, which are not nearly as toxic to koi as ammonia and
nitrites are, we’re felt by many to be harmless to koi for years. More recently however,
studies have found that medium to high levels of nitrates are associated with stress in
koi, along with lowering the koi’s immune system and a number of other serious health
issues. Regular water changes can keep the nitrate level in a pond down to almost zero.
Truly, regular water changes can greatly improve not only the koi’s health but can also
improve the quality and the clarity of the pond’s water.