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How to Do a Jar Test

How to Do a Jar Test

Creating a mini-ecosystem of your pond with a Jar Test will help you diagnose your pond problem. If you have green, tea-colored, or murky water doing the Jar Test will you to determine what is causing the clarity issue.

It's Simple

Take a clear glass jar, dunk it in your pond, fill it up with pond water, and let it sit in your garage (or darker space) for 24 hours. Overnight, the jar becomes a miniature version of your pond.

The Results

Green Water
If your jar contains green-tined water or if the water has green particles in it, you most likely have algae. Planktonic algae – the source of algae blooms – are floating, microscopic plants that color pond water green, blue-green, brown or variations in between. Your jar is telling you to treat for algae.

Tea-Colored Water
Discolored or tea-colored water means you have some leaf tea brewing in your pond. As organic debris decomposes in your pond, the tannins and other byproducts mix into the water column, discoloring it. Your first remedy is to add a bag of Activated Carbon to the water. It will clear up the dissolved materials that are causing the problem. While the carbon is working, remove floating and decaying material with the a Net or use the ClearVac Pond Vacuum. Keep your pond clean by skimming it regularly and covering it with pond netting during the fall months.

Clear Water With Sediment
Does your jar have clear water with a layer of sediment on the bottom? If so, you have an abundance of organics in the pond, and your fish are constantly stirring them up and clouding the water. Here is a four-step solution to get you started:

  1. Remove large debris.
  2. Perform a partial water change.
  3. Add a Water Conditioner.
  4. Double down on the Beneficial Bacteria.

A jar test can reveal a lot about the water in your pond. If you need some assistance in determining what your jar is telling you, email us your Jar Test photo at or use our contact form.