Dosing uses the concentrated-remover standard (1 fl oz per 10,000 gal removes ~100 ppb) — dilute products need far more, so the label wins. Retest 48 hours after the water clears.
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The remover math
fl oz ≈ (ppb to remove ÷ 100) × (gallons ÷ 10,000) target: under ~300 ppb — zero isn't necessary
Lanthanum binds phosphate on contact and the filter does the rest. The dose scales with both the water volume and how far the reading needs to fall, which is why a big pool with a big reading can need a surprisingly large bottle — and why the concentrate is the only economical format for readings past 1,000 ppb.
A worked example
A 15,000-gallon pool at 900 ppb, aiming for 300: removing 600 ppb takes about 9 fl oz of concentrate. Evening dose, pump on overnight, two milky days, one backwash, retest — done for the season unless the fill water restocks it.
Keep it in perspective
Phosphate remover is a supporting actor. The pools that never turn green are the ones holding the right chlorine level for their stabilizer — the chlorine calculator and CYA calculator are that whole story. If you're fighting algae right now, the green pool calculator is the cure; this page is for making the next outbreak less likely.
Frequently asked questions
What phosphate level is too high in a pool?
Under 500 ppb, most pools run fine — don't chase zero. Between 500 and 1,000 ppb is watch territory. Over 1,000 ppb, chlorine has to fight noticeably harder and algae recovers faster from any slip; that's when a remover starts earning its price.
Do I actually need phosphate remover?
Honest answer: a pool with proper chlorine (matched to its stabilizer level) doesn't get algae even with phosphates present — chlorine is the defense, phosphates are just the food supply. Remover is for stacked odds: a pool that keeps drifting green, very high readings, or fill water that arrives loaded.
Why did my pool turn cloudy after phosphate remover?
That's it working. Lanthanum-based removers bind phosphate into a fine white cloud that your filter then catches — expect 24–72 hours of milky water, rising filter pressure, and a backwash or cartridge rinse at the end. Dose in the evening and let the pump run.
Where do phosphates come from?
Fill water (many municipalities add phosphates to protect pipes), lawn fertilizer drift, leaves and pollen breaking down, and some stain-and-scale products (metal sequestrants literally are phosphonates). That's why levels creep back — retest monthly, not daily.