Water Quality    When you appreciate that water is to koi fish like air is to humans, you begin to appreciate why water quality is so important to koi. To illustrate: imagine you had a very slight gas leak in your house. You can’t see the gas and you don’t  recognize the smell, but you find that after a few weeks you don’t feel well. The gas itself is not bad enough to kill you, but your resistance is lowered, because your body has to constantly work to repair the damage the gas is causing. In time you find that you get sick easily, whether it is a cold, the flu or whatever you are exposed to. On the other hand, if the gas leak suddenly got bad enough, it alone could kill you.

It is very similar with fish and pond water. Poor water quality will kill your fish faster than anything else. Low oxygen in a pond can kill every fish in the pond overnight. High ammonia levels can kill fish within several days. But, even marginal levels of oxygen, ammonia and nitrates can set your fish up to fall victim to other life threatening problems. So, the goal should always be to have the best water quality possible. There are basically five water quality items you need to be concerned with, ph, ammonia, nitrite, nitrate and oxygen.