Tannins are great for many things. They give color and mouthfeel to wines and are a source of healthy benefits in teas. One place you don’t want too many of them, though, is in your pond. Tannins come from leaves and other vegetation.
When the leaves get into your pond and start to decompose tannins leach out, making your water a different color. Interesting facts:
- The tannins from decaying leaves and vegetation by a stream can make what is actually called a “blackwater river”.
- Peat tannins (from bogs) can turn the water a brown color.
- When tannins are in your pond they can make the water smell (and taste) bad.
Once the water in your pond has been stained by tannins, just like a cup of tea – the color will not “settle out.” They will have to be chemically or physically taken out. Step one is to take out the leaves from the pond with a net. This means both floating and the ones that have settled to the bottom. Don’t forget to empty your skimmer net regularly. It’s like a giant tea bag, seeping more discolored water.
I’ve found the most effective, fish friendly way to remove the color from the water is Activated Carbon. Put the carbon where there is strong water flow (mine is in the skimmer). The tannins are absorbed by the activated carbon. Once the carbon has absorbed it’s limit, it should be taken out and replaced if needed. If your water is very discolored, a partial water change might be needed.