Cause of high nitrates?
I'm in the middle of turning a 30 gallon fish-only tank into a planted tank. I removed the fish, substrate, almost all of the water - basically everything but the filter. Put Aquasoil Amazonia substrate in, on top of a layer of Power Sand, and added a couple pieces of Malaysian driftwood. I have not put the plants in yet. After letting it sit for 48 hours, I tested the water. The water is tea-colored, which I expected from the driftwood. Well, before I switched the substrate out and took out all the fish, the nitrates had never measured about 10 ppm. Now they're about 30! Nitrites and ammonia are 0, though I suppose that's not surprising since there haven't been any fish in it for two days.
I've never used either driftwood or Aquasoil before. Are either of these the cause of the nitrates, and if so, will it go down with water changes? Has anyone else experienced this?