Ahhhhhhhh! I do have driftwood yes, just put it in, so it'll be that... So is there no way you can have it in a brackish tank and keep the water clean?
Driftwood can leach tannins for years. Expect that there will be a yellowish tint for a while. The only thing that can "fix it" is time. The tannins are harmless, so it's purely aesthetic.