• When water is added or used in the pond it adds chlorine and chloramine to the water which strip the slime coat off fish causing the fish to be susceptible to diseases. It also kills nitrifying bacteria. Use a dechlorinator after all water changes to keep fish healthy. Never do more than a 20% water change per day or the fish will go into shock.

  • Monitoring water quality is the best way to know what is going on in your pond. There are tests that need to be run on a regular basis, at least weekly when things are going well and daily if you suspect problems. You need to test for pH, ammonia, nitrites, nitrates. You can buy test kits at pet stores that will give you these readings conveniently. The pH level for a pond is ideally between 6.8 and 7.4, but higher levels (even up to 9.0) are acceptable. It is more important that the pH level change as little as possible. Chemically altering pH levels is not suggested as it is pH swings that kill fish not the pH level. The hardness of water is the way it buffers the pH. In Utah we have very hard water so testing for hardness needs to be only occasionally or when fish are sick. Nitrate levels should be at 0 as should nitrites. Levels higher than this indicate problems with the ecosystem and danger to plant and fish life.

Once your pond has been constructed the work is not over. There are numerous tasks that need to be done on a regular basis.

The ecosystem

  • A pond is a small ecosystem and any one component that is out of whack will bring the whole system down until it is corrected. It is critical you understand the nitrogen cycle You feed fish food and they excrete ammonia which the nitrifying bacteria eat and convert into nitrtes which other nitrifying bacteria eat and convert into nitrates which is fertilizer for plants and algae which the fish eat. Too much ammonia in the water is like too much carbon dioxide for us (it will kill them). Too much nitrites will kill the fish. Too much nitrates makes algae and anaerobic bacteria grow which deprive the fish of oxygen. So as you can see it is very important to keep all this under control. It sounds complicated and it is, but feeding fish correctly and keeping a clean pond makes the chore fairly simple.

What you should do

  • As in all things in life cleanliness is very important to good health. Decaying plant life deprives the water of oxygen that fish and nitrifying bacteria need. This allows anaerobic bacteria to proliferate which stress the fish, making them susceptible to diseases. Remove dead plants and leaves daily if needed.