Excellent explanation, FF.
Just to add a little personal experience to this - before our current tank, we had a 75g with a
CC bed. I could *never* get the nitrates in this tank below 20-30ppm. Interestingly enough, it was a thriving softy/shroom tank which exhibited *tons* of growth. I would *never* chance this if I were attempting to do
sps - which is the main reason we changed to a
DSB with the 180g.
However, I honestly believe that some softies do better with some level of nutrients in the water - they don't need the absolute pristine conditions that
sps require. I am by no means promoting the use of
CC as a substrate - a
DSB is simply a far superior substrate for a reef tank, for denitrification amongst other reasons. I simply wanted to mention that some softies/
shrooms, etc. can do well in less-than-perfect nitrate levels.
A side note - you mentioned "adding"
LS. As FF mentioned,
CC substrate by nature usually maintains a somewhat elevated nitrate level (due to the grain size/trapping detritus). Adding
LS will not solve this problem - you would need to remove the
CC and replace it with
LS.
as a lime (but learning )
