Planted Tank Guru
Join Date: Nov 2009
Location: Missouri united states
After a few hour's with filter's running?
If filter running for a few hour's does not make improvement, then a few water changes maybe twelve hour's apart at near 50% should.
Maybe clean the filter media after a few day's also and or run some fresh carbon in the filter's for a week and then remove it.(carbon less effective after a week)
Last resort,,rinse ,rinse,rinse,the sand some more.