BioGuard Zero Phos | Pool Phosphate Remover

• 1 x BioGuard Zero Phos, 1 quart (32 fl oz) bottle
• Full manufacturer label with the phosphate dosing chart and application directions

One bottle is a complete treatment for a 20,000-gallon pool at the highest phosphate level on the chart, or up to eight treatments at the lowest corrective level.

Reduces Phosphates in as Little as 24 Hours

Fast corrective action on elevated phosphate levels, rather than a slow drawdown over weeks of maintenance dosing.

Dosing Matched to Your Test Reading

Four defined levels keyed to actual phosphate readings, so the correction is sized to the problem instead of applied as a single generic dose.

Removes the Nutrient Algae Depends On

Takes away the food source before a sanitizer dip becomes a bloom, which is the difference between a pool that recovers from a hot weekend and one that turns green.

Concentrated Formula

A single quart treats a 20,000-gallon pool even at the heaviest correction level on the chart.

Simple Application

Add directly to the skimmer or around the pool edges with the pump running. No pre-mixing, no dilution, no special equipment.

Works With Every Sanitizer Type

Compatible with chlorine, bromine, salt chlorine generator, and mineral system pools, on all common surfaces and filter types.

Protects Salt Generator Cells

Phosphates contribute to scaling on chlorine generator cells, so lowering them protects the equipment as well as the water.

Phosphates in pool water are dissolved and chemically stable. They aren't organisms, so sanitizer doesn't destroy them. They aren't particles, so a filter can't catch them. They aren't volatile, so they don't evaporate. Left alone, the level only goes one direction.

Zero Phos works by binding phosphate ions into an insoluble compound. Once phosphate is converted from a dissolved state into a solid particle, it becomes something your filter can physically capture and remove from the pool. That's genuine removal rather than suppression — the phosphate leaves the water entirely and stays gone until new phosphate enters.

This mechanism explains the two things people find surprising about the product.

First, the water often goes cloudy immediately after application, and the label says so directly. That cloudiness is the phosphate, now converted into suspended solid. On a pool that's been accumulating phosphates for a season or more, that's a substantial amount of new material appearing in the water at once. It looks like the product made things worse. It didn't — the haze is proof it worked, and it clears within 48 hours as the filter removes it.

Second, the filter does the actual removal, which is why the directions specify continuous circulation for 24 to 48 hours and backwashing afterward. The product converts the phosphate; the filter takes it out. Shut the pump off early and the converted phosphate stays in the pool. It's also why filter pressure rises during treatment — the media is loading up with what it just captured.

One point about scope: Zero Phos is not a sanitizer, an algaecide, or a clarifier. Removing phosphates makes algae far less likely to establish, but it does not kill algae that's already growing. A pool that's currently green needs shock and an algaecide first; Zero Phos is what keeps it from happening again.

It's also worth knowing that some pool products add phosphates. Certain sequestrants and metal-control products are phosphate-based, which is why a pool on continuous metal treatment can show rising phosphate levels despite good housekeeping.

Pro Tip: Expect the water to cloud, and don't reach for a clarifier when it does. This is the most common support call on any phosphate remover. The haze is dissolved phosphate converting into filterable solid — exactly what you paid for — and it clears within 48 hours as the filter pulls it out. Adding a clarifier on top just loads the filter faster. What actually helps is running the pump continuously, watching the pressure gauge, and backwashing when it climbs 8 to 10 psi above your normal operating pressure. Then backwash again at the 48-hour mark whether pressure has risen or not.

Dosage by Phosphate Reading — per 20,000 Gallons

• 0–125 ppb: acceptable range — no treatment needed
• 126–500 ppb: use BioGuard Pool Complete Weekly instead
• 501–1,000 ppb: 4 fl oz
• 1,001–2,000 ppb: 8 fl oz
• Over 2,000 ppb: 32 fl oz

Maximum dose for pools under 10,000 gallons: 16 fl oz, regardless of reading.

Before You Start

1. Test phosphates and record the reading — the entire dose depends on it.
2. Make sure all pool equipment is working properly, including the pump, filter, skimmer, and heater.
3. Backwash and rinse the filter according to your equipment manufacturer's instructions. The filter has to be clean, because it's what removes the converted phosphate.
4. Note your normal operating filter pressure so you have a baseline.
5. Confirm your pool's actual gallon capacity before measuring.

Application

1. Apply BioGuard Zero Phos directly to the skimmer or around the edges of the pool, at the amount matching your phosphate reading. For pools under 10,000 gallons, do not exceed 16 fl oz.
2. Allow the pump and filter to run continuously for 24 to 48 hours. Pool water may cloud upon addition but will clear within 48 hours.
3. If filter pressure increases 8 to 10 psi above normal operating pressure, backwash and rinse the filter.
4. After 48 hours, backwash and rinse the filter according to your manufacturer's instructions.
5. Retest phosphates to confirm the treatment worked, or to determine whether another application is needed.
6. Repeat if levels remain elevated.

After Treatment

• Once phosphates are in the acceptable range, switch to weekly maintenance with Pool Complete Weekly to keep them there
• Retest phosphates periodically through the season, especially after heavy rain or runoff
• Confirm sanitizer and balance are back in range after the filter work

When to Use It

• A phosphate test reads above 500 ppb
• Recurring algae blooms with no obvious cause despite adequate sanitizer
• At opening, after a winter of accumulated runoff and debris
• After heavy rain or irrigation runoff carrying lawn fertilizer
• Following an algae treatment, to remove the nutrients that fed the bloom
• On a salt pool where cell scaling is a recurring problem

Storage and Handling

• Store in a cool, dry, well-ventilated area, out of direct sunlight and protected from freezing
• Keep the container tightly closed and clearly labeled
• Store separately from sanitizers, acids, and oxidizers
• Keep out of reach of children and pets
• Read and follow all label precautions, first aid, and disposal directions before use

Pro Tip: Correct once, then maintain — don't keep buying the corrective product. Zero Phos is built to bring a high reading down fast, and it's the right tool for that job. But once phosphates are back in the acceptable range, holding them there costs far less with a weekly maintenance product than with repeated corrective treatments. BioGuard's own chart makes the handoff explicit: readings between 126 and 500 ppb are routed to Pool Complete Weekly rather than Zero Phos. Correct the problem, then switch to the weekly routine, and you'll likely never need the corrective bottle again unless something unusual happens — a major runoff event, a long stretch of neglect, or a new fill.

• Brand: BioGuard
• Product Type: Concentrated phosphate remover
• Form: Liquid
• Volume: 1 quart (32 fl oz)
• Manufacturer Part Number: 25769BIO
• Function: Reduces elevated phosphate levels
• Speed of Action: Reduces phosphates in as little as 24 hours
• Acceptable Phosphate Range: 0–125 ppb
• Dose at 501–1,000 ppb: 4 fl oz per 20,000 gallons
• Dose at 1,001–2,000 ppb: 8 fl oz per 20,000 gallons
• Dose above 2,000 ppb: 32 fl oz per 20,000 gallons
• Maximum Dose Under 10,000 Gallons: 16 fl oz
• Readings 126–500 ppb: use BioGuard Pool Complete Weekly instead
• Circulation After Application: 24–48 hours continuous
• Application Method: Add directly to the skimmer or around the pool edges
• Expected Cloudiness: Water may cloud on addition; clears within 48 hours
• Filter Backwash: At 48 hours, or sooner if pressure rises 8–10 psi above normal
• Follow-Up: Retest phosphates to confirm results
• Filter Compatibility: Sand, cartridge, and DE
• Sanitizer Compatibility: Chlorine, bromine, salt generator, and mineral systems
• Suitable Surfaces: Plaster, gunite, vinyl liner, fiberglass, painted
• Not A Substitute For: Sanitizer, algaecide, or water balancing
• Shipping Classification: DOT-regulated — ground shipping only

Pool Types and Surfaces

• In-ground and above-ground pools
• Plaster and gunite
• Vinyl liner
• Fiberglass
• Painted surfaces

Sanitizer Programs

• Chlorine pools — fully compatible
• Bromine pools — fully compatible
• Salt chlorine generator pools — fully compatible and particularly worthwhile, since phosphates contribute to cell scaling
• Mineral system pools — fully compatible

Filtration Systems

• Sand, cartridge, and DE filters — the filter is what physically removes the converted phosphate, so it must be clean and running

Zero Phos Versus Pool Complete Weekly

• Zero Phos is the corrective product. Use it when a test shows phosphates above 500 ppb and you need levels down quickly.
• Pool Complete Weekly is the maintenance product. Use it weekly to keep phosphates from accumulating in the first place, along with clarifying and waterline protection.
• BioGuard's own dosing chart routes readings of 126–500 ppb to Pool Complete Weekly rather than to Zero Phos, so the two products have defined, non-overlapping roles.
• The typical sequence is Zero Phos to correct, then Pool Complete Weekly to hold the line.

Where Phosphates Come From

• Rain and irrigation runoff carrying lawn fertilizer
• Decaying leaves, grass clippings, and organic debris
• Swimmer waste, body oils, and cosmetics
• Source water — some municipal supplies add phosphate as a corrosion inhibitor
• Phosphate-based sequestrants and metal-control products

What It Does Not Do

• Not a sanitizer. Provides no disinfection and maintains no residual.
• Not an algaecide. It removes the food source but will not kill existing algae. A visible bloom needs shock and an algaecide first.
• Not a clarifier. It will temporarily cloud the water rather than clear it.
• Not a substitute for water balance or sanitation.

Important Handling Cautions

• Never mix with other chemicals. Add products separately with circulation between additions.
• Do not exceed 16 fl oz in pools under 10,000 gallons, regardless of the phosphate reading.
• Expect filter pressure to rise during treatment; backwash at 8–10 psi above normal.