I've had my huge tank running for about 3 - 4 months and can't get the nitrates to go down bellow 20. Its fOLR as of now, but by next week i plan to get some softies. Is it safe to do that? Everything else i tested is perfect except the nitrates around 20-30. I thought about that sulfur denitrifier, but couldn't i just add more clams? Anyone know how many clams i need to drop nitrates down to 0-5?