How to Control Green Water Algae

Green water is caused by single-cell algae that thrives on excess nutrients in the pond – specifically nitrites.

While you can buy algaecides, UV sterilizers and other products to kill the algae, your first line of defense should be to eliminate the algae’s food source. This method prevents new algae from forming, saving you time and money in the long run.

Step 1: Remove Excess Debris

Remember those nitrites we talked about, the stuff that feeds the green water algae? These nitrites are a natural byproduct of your pond’s nitrogen cycle, in which beneficial bacteria break down ammonia and other potentially harmful compounds.

If you want fewer nitrites in your pond, you need to reduce the ammonia load. And the best way to do this is by removing as much organic material from the pond as possible before it has a chance to sink to the bottom and decay. That’s where a pond skimmer comes in.

A pond skimmer will remove most large leaves and other stuff from the pond before it has a chance to interact with your pond’s ecosystem.

Step 2: Grow Nitrite-Eating Bacteria

Even with a skimmer, your pond ecosystem will still produce some nitrites. Your next step is to get rid of these nitrites before the single-cell algae has a chance to chow down. The best way to do this: add lots of beneficial bacteria.

Beneficial bacteria are microorganisms that grow naturally in your pond’s gravel, biofilter and other nooks and crannies. If you have enough of them, they’ll eat excess nitrites before algae has a chance to get to it. The end result: Existing algae starves, and there aren’t enough nutrients left in the pond to support new algae growth.

Here are the steps you should take to support beneficial bacteria growth in your pond:

  • Make sure you have adequate biological filtration in the form of a BioFilter.
  • Add regular doses of additional bacteria to the pond via a squirt bottle or automatic dosing system.

The Bottom Line on Green Water

Green water generally won’t hurt your fish, but that doesn’t mean you have to deal with it. With good filtration and regular doses of beneficial bacteria, you can keep your water crystal-clear.