Q. I’ve noticed that there are test kits for sale at my local water garden center. When is it necessary to actually such kits? My pond seems fine to me, but I assume the kits are available for a reason.
A. It is unfortunate that most pondkeepers do not use or even own test kits. The first and probably most important step in preventing fish health problems is understanding the basic water chemistry of the pond water.
Every pondkeeper should own at least four test kits: ammonia, nitrite, pH and dissolved oxygen. These kits are not expensive, and certainly cost far less than the value of the koi that many ponds contain. The dissolved oxygen test kit is somewhat more expensive than the others, but its value is obvious if you read my answer to the first question in this month’s column.
A properly maintained pond for koi or goldfish will have a pH between 6.5 and 7.8, although a pH of up to 8.4 will not harm the fish. Its values below 6.5 that you should be concerned with. As for ammonia and nitrite levels, they should be unmeasurable with the kinds of test kits sold to hobbyists. Dissolved oxygen should be at least 6 parts per million regardless of the water temperature.