Why it matters
Even small amounts of phosphate in a reef tank cause coral browning and pale tissue. In pools, phosphate feeds algae and consumes chlorine.
Ideal ranges
| Water type | Ideal | Acceptable |
|---|---|---|
| Reef | 0.02 to 0.10 ppm | — |
| Freshwater planted | 0.5 to 1.5 ppm | — |
| Pool | below 100 ppb | — |
- Reef: Zero phosphate starves coral. Some is essential.
How to test
- 1
Reef: Hanna ULR Phosphate Checker
Reads to 0.001 ppm. Salifert is acceptable but coarser.
- 2
Pool: PhosKill or strip test
Strips read in 100 ppb increments.
How to correct high phosphate
Reef: dose lanthanum chloride or run GFO
Start with 25 percent label dose. Drop too fast and coral suffers.
Pool: add phosphate remover
Brand-name treatments precipitate phosphate so the filter catches it. Clean filter after.
Reduce feeding and address dead spots
Phosphate often comes from rotting food or detritus pockets.
Common causes
- •Tap water with phosphate
- •Overfeeding
- •Decaying matter
- •Some pool stain treatments contain phosphate
FAQs
My reef has zero phosphate. Is that good?
No. Coral needs trace phosphate. Aim for 0.03 to 0.08 ppm. Pale tissue and slow growth are signs of starvation.