I bought a piece of driftwood with a plant in it on clearance at Petsmart. I removed the crappy plant but put the driftwood into my 29-gallon freshwater planted tank (it had come straight from the Petsmart tank and had been soaking there for a while, so I figured it would be okay in mine).
Recently, I noticed my diamond tetras looked different, discolored somehow. I decided to do a big water change, about 50%, and in doing so, I took out the driftwood and stored it in my son's guppy tank. I noticed the water I was removing had a yellow tint, but I didn't think much of it. For a week, things perked right back up. My tetras looked their shiny silvery selves. My water sprite was growing better and so was the wisteria. However, my Siamese Algae Eaters had taken to hiding in a resin log. I read up on them and discovered they needed bogwood, which I figured was driftwood, so I put the driftwood back in.
Within 24 hours, the water was yellowish again, my diamond tetras look weird, and even the plants darkened up. I Googled, learned driftwood can leach tannins and change water color, but I could not find anything on whether it affects fish color or plants.
I am going to do another water change right now, but I would like to know if it's the driftwood which is affecting the plants and fish. It seems logical, but I doubt my own brain nowadays.