I recently removed all the live rock, corals and sand from my system (91-gal.). I replaced the same volume of sand with CaribSea Aragonite Hawaiian Black sand. I also have three 4" MarinePure blocks in the sump that have been there for a long time. I did two 40% water changes over the weekend before adding the sand.
KH, Ca, Mg are all within normal range. My Nitrates have run between 4 ppm - 8 ppm over the last few months. But my Phosphorus had a huge spike. It's been running around 50 ppb before the water change and new sand. A couple days later it's at 105 ppb (0.32 ppm phosphate).
I understand <100 ppb is acceptable for a fish only system so I'm not in dire straights. But I'm curious why it doubled after the aforementioned. Is it because there are no corals or algae to absorb the phosphorus? Will it decrease through water changes perhaps leeching out of the sand if that's the cause?
KH, Ca, Mg are all within normal range. My Nitrates have run between 4 ppm - 8 ppm over the last few months. But my Phosphorus had a huge spike. It's been running around 50 ppb before the water change and new sand. A couple days later it's at 105 ppb (0.32 ppm phosphate).
I understand <100 ppb is acceptable for a fish only system so I'm not in dire straights. But I'm curious why it doubled after the aforementioned. Is it because there are no corals or algae to absorb the phosphorus? Will it decrease through water changes perhaps leeching out of the sand if that's the cause?
