Can anyone tell me why my Bogwood discolours sand in my tank please?

Question

I have several tank but i have always wondered why my bogwood is discolouring my sand at the bottom of my tank. The thing is, I have cleaned it and soaked it when I first bought it two or three weeks back. I always remove the sand and replace it with washed sand. I hope it isnt harmful to the fishes, although no complaints from them but I am am always curious and want to have my tank tip top shape. Thank you all x

Answer 1

It could be leaching tannins, but these are water soluble, so they shouldn't stain the sand.

Wood is a natural substance so it contains many other chemicals. One is a small amount of iron, so if the rocks are being stained a "rust" color of brown, I'd say iron was responsible.

If the stain is a darker brown-black, since you're using sand as a substrate, there may not be enough oxygen getting to the areas beneath the wood and you're getting a little reaction from anaerobic bacteria and manganese.

Both stains would be soluble in acids, but this would require removing the sand that's stained and treating it outside the tank. Increased water circulation can prevent more of the manganese stain from forming. If the wood is leaching iron, there's not much (practical) that can be done, but aquatic plants may help hide the stain (and since aquatic systems are iron-deficient, live aquatic plants would love this environment if your lighting would support them).

Neither of these, in small amounts, would harm your fish.

Answer 2

both above answers are correct, I had some in my tanks years ago and had to soak 10 times in fresh water each time before it was suitable for my tank

Answer 3

Your wood is leaching tannins. It isn't particularly harmful to your fish.

Below is a website that describes how to prep bogwood for an aquarium so it won't leach so much tannin.