Like tannin brown or diatom brown? I've got MGOPM capped with black diamond in two tanks. The bigger one is high light with stems and is messed with all the time. Actually, much of it no longer has much of a cap. The water is usually crystal clear. The smaller tank had some tannin looking water sometimes during the first month but looked fine after a 50% water change. I didn't bother filtering out the smaller pieces of wood in the MGOPM so figured it probably was tannins.
I don't know the answer to your question but maybe my above experience will help.
Do you have driftwood in the tank?
I don't know the answer to your question but maybe my above experience will help.
Do you have driftwood in the tank?