Sometimes in your koi pond you will see a haze.

There are two types of haze: a milky gray or brown type and a green type.

  • The milky gray or brown type usually shows up immediately after you put rocks or aggregate in the pond, or right after it’s built. This is a mineral haze which is basically just micro-particles of gravel, sand, and other items used in pond construction. This type of haze is not good for your fish.

Their slime coat is rather absorbent and as a result, the mineral particles will stick to your fish. Never put fish in an environment with a mineral haze. When you first build your pond, wait until the haze is gone before adding your fish. You can clear the mineral haze with an ultraviolet sterilizer.

  • Another type of haze is a bacterial haze which makes the water cloudy and has an odd, organic-type smell. Bacterial haze can kill your fish. To get rid of it:
  1. The first thing you should do is immediately suspend feeding.
  2. The second thing is to clean your filter and possibly consider upgrading to a larger filter.
  3. The third thing to look at is crowding; you should only have one inch of fish per ten gallons of water.

If your koi pond stocking density is higher than this, then you should consider cutting down on your koi fish. The fourth thing to do is check for uneaten food and net it out if there is any.

You should also check for dead fish or any other decaying material in the koi pond that could cause a bacterial haze. If you have sponge filtration and good aeration, you can use a water clarification product to remove the bacterial haze.

The bottom line is mineral and bacterial hazes are harmful to your fish. Follow the above steps to remove such hazes from your koi pond.

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