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High Phosphate in Reef Tanks: What to Do and What to Avoid

High phosphate in a reef tank

Phosphate is a normal nutrient, but when it gets too high it often fuels algae and can stall coral growth. The key is controlled reduction.

Common signs

  • Algae growth that returns quickly
  • Darkening or muted coral colour
  • Phosphate test results staying elevated

Common causes

  • Overfeeding
  • Old media or trapped detritus
  • Leaching from rock or sand
  • Weak export or inconsistent maintenance

A safe plan that actually works

  1. Confirm the reading (retest and check expiry dates).
  2. Clean up detritus traps and refresh mechanical filtration.
  3. Reduce phosphate slowly and avoid aggressive stripping.
  4. Re-test 24 hours after dosing adjustments, then dial in your routine.

Recommended product: Phosphate Reducer

  • Binds free phosphate for controlled reduction
  • Helps reduce algae pressure and stabilise nutrients
  • Designed for reef safe use when dosed correctly

Shop Phosphate Reducer

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