Old wood branch and water becomes dark brown. Ok for gourami?

[Aniket]

I placed wood in extra tank and water became dark brown. I wanted to move my gourami from main tank because he got white spots. So can i move him in dark brown water? Or i have to change water?

 

[evanb]

Whenever I am putting a piece of wood into a tank I always fully submerge the piece in a bucket for a few days. The water will still turn slightly brown once it's in the tank but after a few water changes it should start to improve the clarity of the water.
When wood is in a fish tank the water will generally be slightly yellowish/brown due to the tannins released. It doesn't harm the fish in any way in fact it can actually be good for them. Also it can give the aquarium a more natural look. Tannins lower the PH of the water and soften it.

 

[Colin_T]

If one fish in the tank has white spot, then all the fish will have it. Leave the gourami in the tank until after you have finished treating the white spot, then move it.

Yes you can move fish that are in black water (tannin stained water).