I've noticed this a bit ever since I set the tank up but it's becoming more pronounced. The water has a slightly yellow/brown discolouration to it. It's noticeable when you look at the tank but it's more noticeable when I do my weekly water changes.
I have a very old piece of driftwood in the tank. It was a piece originally purchased at a fish store and it was intended for aquarium use. My dad purchased it for his aquarium 20+ years ago, and only used it briefly. It has for the last 18+ years sat at his house. Could the colour be leeching off the wood and into the water?
The only other thing I'm thinking could be the cause is my sand substrate. I'm using black tahitian moon sand, and i thought I cleaned it thoroughly. i cleaned each bucket full until the water ran clear, but is it possible that this wasn't enough and some colour is coming off of it? When I first began cleaning it, the water ran jet black, so it did give alot of colour.
Or could it be something else entirely? I use all silk plants and the only other decoration I have in the tank are decorative stones. All my ammonia, nitrite, nitrate, and pH readings are as they should be and all the fish appear to fine.