Bound Phosphate
Bound phosphate is phosphate that has combined with calcium, forming tri-calcium di-phosphate (Ca₃(PO₄)₂). The Aqua Care Guide™ calls it chemically bound phosphate.
It isn’t part of the water column, so common phosphate tests can’t detect it. They only read ionic phosphate (PO₄³⁻), the other main form.
Why It’s Important
- Phosphate bound with calcium can settle onto your live rock.
- Algae and bacteria can still use that calcium and phosphate. The Guide says that’s often why a tank reads low phosphate and still has problems.
- Calcium locked up this way leaves the water column, which lowers calcium and can stress corals.
- Dosing more calcium to make up for it can create more bound phosphate.
How It Works
AR Phosphate Remover™ removes both ionic and chemically bound phosphate, at all ranges, and frees up bound calcium.
The Guide notes that as phosphate falls, dosing no longer follows a straight line. That’s mainly because the bound phosphate is being removed too.
Bound Phosphate and Related Terms
Bound phosphate is one form of phosphate, the compound of phosphorus that fuels algae. It forms through precipitation with calcium and collects on live rock.
Common Misconception
A low phosphate reading doesn’t always mean phosphate is under control. Bound phosphate doesn’t show up on a standard test.
The Bottom Line
Bound phosphate hides on rock and out of test range, and it can keep fueling algae. Read Understanding Phosphate in Aquariums for the bigger picture.