Using Driftwood and Coconuts to Change Water Acidity

Q&A about using drifwood to change freshwater aquarium water acidity.

Q. I have a 50-gallon tank and would eventually like to own discus. I have heard that you should add driftwood or coconut shells to a discus tank to make it more acidic, due to tannins. I have also heard that for fish needing alkaline water, you can boil the coconuts to remove the tannins, but would this be bad for my setup? Should I boil them a little for sanitation purposes but still let the water go “black” to be more like the natural water?
Forrest Phillips
Alexandria, Virginia

A. Driftwood is a wonderful decoration for freshwater aquariums. It adds natural beauty to the aquatic environment, and no two pieces are alike. Coconut shells — usually half-shells — are sometimes used by hobbyists to create spawning caves for fish or to provide cover for shy species. These wooden decorations have the ability to release substances as they break down, especially tannins, which can help soften and acidify the water. Tannins can color the water yellow to brown like tea. This darkened, soft, acidic water is often called “blackwater” because deep rivers of this type appear black.

Discus prefer soft, acid water and are found in blackwater habitats in the wild. Many hobbyists use peat, driftwood or coconut shells to help duplicate this effect. Do not boil your wooden decorations, unless you want to reduce or destroy their ability to leach tannins and color the water. The degree of leaching varies greatly. Malaysian driftwood probably leaches the most tannins, followed by African driftwood (sometimes called “mopani wood”). Both of these are self-sinking, too. The American driftwoods that sell attached to a slate base (to help them sink) leach very few tannins. I’ve never used coconut shells, though, so I don’t know where they fall on the scale. Happy fishkeeping!

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Fish · Lifestyle