BioGuard Arctic Blue Shock | Winter Pool Shock

• 1 x BioGuard Arctic Blue Shock, 2 lb bottle
• Full manufacturer label with dosing rates, application directions, and safety information

Note on quantity: at 1 lb per 6,000 gallons, a 2 lb bottle treats up to 12,000 gallons. A 20,000-gallon pool needs two bottles, and a 25,000-gallon pool needs three. Calculate your total before ordering — running short mid-closing means the treatment doesn't get finished.

First Step in an Effective Winterization Program

The opening move in the BioGuard Arctic Blue closing sequence, applied before the winterizing algaecide and the final closing treatment.

Oxidizer, Buffer, and Clarifier in One

Handles three closing jobs from a single application — burning off the organic load, moderating water chemistry, and clearing suspended material before the cover goes on.

Makes Spring Opening Easier

Helps avoid the costly spring problems that come from a poorly closed pool: algae, high chlorine demand, and cloudy water that takes weeks and multiple products to resolve.

Restores Water Clarity

Produces clear water going into the off season and coming out of it, rather than a pool that spends the winter hazy.

Quick-Dissolving, No Dilution Needed

Broadcasts directly from the bottle into the water. No bucket, no pre-mixing, and no handling of liquids in cold weather.

Ideal for All Pool Surfaces

Suitable for plaster, gunite, vinyl liner, fiberglass, and painted finishes.

Works With Multiple Sanitizer Systems

Compatible with chlorinated, brominated, ozone, and ionization pools.

Made in the USA

Manufactured domestically under BioGuard's quality standards.

The active ingredient is sodium dichloro-s-triazinetrione at 58.2% — dichlor. On contact with water it releases hypochlorous acid, the active form of chlorine that oxidizes organic material.

The job at closing is oxidation rather than sanitation. Over a swim season, a pool accumulates a substantial load of non-living organic matter: perspiration, body oils, sunscreen, lotions, cosmetics, and the nitrogen compounds that bind with chlorine to form chloramines. During the season a weekly shock keeps that load in check. At closing, the goal is to burn it down as far as possible, because whatever remains will sit in the water for months with nothing circulating and no sanitizer being replenished.

That organic load is what drives the two most common spring problems. High chlorine demand at opening means the pool consumes shock without holding a residual — the chlorine is being spent oxidizing everything that decomposed over the winter instead of sanitizing. And that same decomposing material feeds algae, which has months to establish under a cover with no chemistry holding it back.

The clarifying component gathers fine suspended particles into masses the filter can capture during the final hours of circulation before shutdown. The buffering component moderates the water's chemical response, keeping the closing treatment from driving a sharp swing in balance right as the pool goes dormant.

An important point on scope, and one where marketing language and the manufacturer's label diverge: BioGuard specifies that this product is not a sanitizer or algaecide. It's an oxidizing shock. It does substantial work reducing the organic load and the conditions algae needs, but the label directs you to follow it with a dedicated winterizing algaecide — and that step is not optional. The shock cleans up what's there; the algaecide guards the months ahead.

One handling note follows from the chemistry: do not pre-dissolve this product. It's applied directly from the bottle into the water, and it must never be mixed with any other pool chemical, where violent reactions can occur.

Pro Tip: Order of operations decides whether a closing works. Balance the water first — total alkalinity, then pH, then calcium hardness. Clean the pool thoroughly and brush the waterline. Then apply Arctic Blue Shock and circulate. Then the winterizing algaecide. Then your final closing treatment. Circulate at least 30 minutes between the shock and the next step, and several hours or overnight is better. Applying an algaecide into water that's still working through a fresh shock wastes a meaningful share of it, because high free chlorine degrades many algaecide actives before they can establish a residual.

Dosage Reference

• 1 lb per 6,000 gallons of pool water
• A 2 lb bottle treats up to 12,000 gallons
• Confirm your pool's actual gallon capacity and order accordingly

Before You Start

1. Confirm all pool equipment is operating properly, including pump, filter, skimmer, and heater.
2. Backwash or clean the filter following your equipment manufacturer's directions.
3. Balance the water — correct total alkalinity, then pH, then calcium hardness.
4. Clean the pool thoroughly: vacuum debris and brush all surfaces including the waterline.
5. Confirm water temperature is consistently below about 60°F.

Application

1. Broadcast the entire dosage into the deep end of the pool with the pump running. Do not pre-dissolve.
2. Brush any undissolved product off the surface of the pool with a compatible brush, to prevent damage to the pool surface.
3. Continue to circulate the pool for a minimum of 30 minutes before proceeding to the next step in the winterization process. Several hours, or overnight, is better.
4. It is recommended that as part of the closing procedures, a quality winterizing algaecide be applied following the application of this product.
5. Complete your remaining closing steps, lower the water level as required for your cover type, winterize equipment and plumbing, and install the cover.

Mid-Winter Treatment

For mesh covered or non-covered pools, a mid-winter treatment may be required using an appropriate BioGuard sanitizer. Mesh covers let sunlight and debris through, so those pools accumulate organic load and lose protection over the off season in a way that solid-covered pools don't. If your pool has a mesh cover, plan on checking it partway through the winter rather than assuming the closing treatment carries all the way to spring.

Storage and Handling

• Store in a cool, dry, well-ventilated area away from direct sunlight, heat, and open flame
• Keep the container tightly closed and the product completely dry — moisture degrades granular chlorine
• Store separately from other pool chemicals, especially calcium hypochlorite shock, acids, and organic materials
• Keep out of reach of children and pets
• Never return unused product to the bottle once it has contacted anything else
• Avoid breathing dust; broadcast downwind of yourself on a breezy day
• Read and follow all label precautions, first aid, and disposal directions before use

Pro Tip: Buy the whole closing set at once, and measure your pool before you order. A closing has a fixed sequence — shock, then algaecide, then closing treatment — and discovering mid-afternoon that you're a bottle short means either an unfinished closing or a pool sitting shocked and unprotected while you make a trip. At 1 lb per 6,000 gallons, a 20,000-gallon pool needs two bottles of shock alone. Work out your gallonage once, write it on a tag in the equipment shed, and you'll never have to guess again — at closing, at opening, or any time you dose anything all season.

• Brand: BioGuard
• Product Type: Winterizing shock — oxidizer, buffer, and clarifier
• Form: Quick-dissolving granular
• Net Weight: 2 lb
• Manufacturer Part Number: 24298BIO
• Active Ingredient: Sodium dichloro-s-triazinetrione, 58.2%
• Other Ingredients: 41.8%
• Dosage: 1 lb per 6,000 gallons
• Coverage per Bottle: Up to 12,000 gallons
• Application Method: Broadcast directly into the deep end — do not pre-dissolve
• Circulation After Application: Minimum 30 minutes; overnight preferred
• Required Next Step: A quality winterizing algaecide
• Recommended Closing Temperature: Water consistently below about 60°F
• Stabilized: Yes — dichlor contributes cyanuric acid to the water
• Suitable Surfaces: Plaster, gunite, vinyl liner, fiberglass, painted
• Sanitizer Compatibility: Chlorinated, brominated, ozone, and ionization systems
• Not For Use In: Biguanide-sanitized pools
• Not A Substitute For: A sanitizer, an algaecide, or water balancing
• Mesh or Uncovered Pools: A mid-winter treatment may be required
• Country of Manufacture: United States
• 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 Systems

• Chlorinated pools — compatible
• Brominated pools — compatible
• Ozone systems — compatible
• Ionization systems — compatible
• Salt chlorine generator pools — compatible; a salt pool is a chlorine pool

Critical Incompatibility

• Biguanide pools — do not use. Chlorine destroys biguanide sanitizer, producing cloudy water, filter fouling, and a failed residual. Biguanide programs have their own closing chemistry.

The Arctic Blue Closing Sequence

• Arctic Blue Shock — first. Oxidizes, clarifies, and buffers. This product.
• A winterizing algaecide — second. Provides the algae protection the shock does not.
• A closing treatment — last. Clarifies, prevents waterline buildup, and removes phosphates before the cover goes on.

All three steps are part of a complete closing. The shock alone does not winterize a pool.

What It Does Not Do

• Not a sanitizer. BioGuard specifies this directly. It provides no lasting disinfection.
• Not an algaecide. A dedicated winterizing algaecide is a required follow-up step.
• Not a substitute for water balance. Alkalinity, pH, and calcium hardness must all be corrected before closing.

Important Handling Cautions

• Do not pre-dissolve. Apply directly from the bottle into the water.
• Do not mix directly with any other pool chemical — violent reactions can occur. Add each product separately with circulation between.
• Never allow undissolved granules to rest on pool surfaces. Brush them off.
• Store separately from calcium hypochlorite shock, acids, and organic materials.