BioGuard Back Up 2 Algaecide | Algae Preventative

SKU: 23050BIO
$29.99

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Description

BioGuard Back Up 2 is the algae preventative BioGuard builds its own care system around — a concentrated quaternary ammonium algaecide designed to stop algae before it ever becomes visible, at a weekly dose small enough that prevention costs almost nothing.

What separates it from a basic algaecide is the surfactant, or wetting agent, built into the formula. Algae doesn't start in the middle of your pool. It starts in the places water barely moves and chemistry barely reaches: hairline cracks in plaster, grout lines, the seam behind a ladder, the underside of a step, the shaded corner of a deep end. A surfactant lowers surface tension so the treatment penetrates into those crevices instead of flowing past them. That's why the product is described as forming a barrier rather than simply floating in the water column.

Two more properties matter through a hot summer. It's stable in sunlight and won't evaporate, so the residual survives the conditions that break down weaker treatments. And its activity increases as water temperature rises — which is exactly backwards from how most people expect a chemical to behave, and exactly right for a pool. Algae grows fastest in hot water, so a preventative that gets stronger as the water heats up is strongest precisely when the pressure is highest.

It's also non-staining and won't affect pH, so weekly use doesn't accumulate metals on your plaster or drag your balance around. And there's a dedicated vacation rate for leaving a pool unattended, which is the situation that turns a clear pool green faster than any other.

One honest caveat before you buy: this is a quat-based algaecide, and quats foam. You may see temporary foaming after application, particularly in pools with fountains, waterfalls, spillovers, or other water features. It clears on its own, but it's worth expecting rather than being surprised by.

Pro Tip: Prevention costs about a ninth of remediation, and the label numbers make the case better than any sales pitch. Weekly prevention runs 1.5 fl oz per 10,000 gallons. Clearing visible algae takes 13.5 fl oz per 10,000 gallons — nine times the product, plus a shock treatment, plus brushing, plus 24 hours of waiting, plus vacuuming out the dead algae afterward, plus a pool nobody can swim in while it happens. A full season of weekly dosing costs less than one recovery. Set a recurring reminder and stay on it.

Brand

BioGuard®

What's in the Box
  • 1 x BioGuard Back Up 2 Algaecide, 1 quart (32 fl oz) bottle
  • Full manufacturer label with dosing rates for all applications and safety information

At the weekly preventative rate, one quart treats a 20,000-gallon pool for roughly ten weeks.

Key Features

Powerful Surfactant and Wetting Agent

Penetrates the tiny cracks, crevices, grout lines, and dead spots where algae actually begins, rather than treating only the open water. This is the defining feature of the formula and the reason it works as a preventative barrier.

Stable in Sunlight, Won't Evaporate

The residual persists through direct sun and heat instead of dissipating, so protection stays in the water between weekly doses.

Gets Stronger as Water Warms

Activity increases with rising water temperature — meaning the product is most aggressive exactly when algae pressure peaks in midsummer.

Low Weekly Maintenance Dose

Just 1.5 fl oz per 10,000 gallons every 5 to 7 days. A season of prevention costs very little, which is what makes staying on schedule realistic.

Non-Staining

Contains no copper or other metals, so weekly use won't deposit staining on plaster, vinyl, or fiberglass the way metal-based algaecides can if conditions drift.

Won't Affect pH

Adding it doesn't move pH or total alkalinity, so there's no rebalancing cycle triggered by your algae program.

Dedicated Vacation Rate

A specific dosing rate for pools left unattended, calculated per week away. An unwatched pool in August is the classic way an owner returns to a green one.

Works as Preventative or Treatment

Separate label rates cover start-up, weekly prevention, heavy bather load, vacation coverage, and clearing visible algae — one bottle handles every scenario.

Preferred Algaecide for the BioGuard Care System

Formulated to complement swimming pool sanitizers rather than compete with them chemically.

How It Works

The active ingredient is alkyl dimethyl benzyl ammonium chloride — a quaternary ammonium compound, or quat, in a blended chain-length formulation of roughly 50% C14, 40% C12, and 10% C16. Different chain lengths are effective against different organisms, so blending them broadens the range of algae the product controls rather than optimizing against a single type.

Quats attack algae physically rather than metabolically. Each molecule carries a positive charge on one end and a long fatty tail on the other. Algae cell walls carry a negative surface charge, so the charged end is drawn straight to the cell, and the fatty tail then inserts itself into the cell membrane. Enough of them embedded in the membrane and it loses integrity — the cell leaks its contents and dies. It's a mechanical failure, not a poisoning, which is why algae doesn't develop resistance to quats the way it can to some other treatments.

That same molecular structure is what makes quats surfactants. A molecule with a water-loving end and an oil-loving end is the definition of a surfactant, so the algae-killing chemistry and the crevice-penetrating wetting action are the same property viewed two different ways. It also explains the foaming: surfactants lower water's surface tension, and lower surface tension means bubbles that don't pop as readily. The foaming is a side effect of the exact mechanism that makes the product work.

Because quats don't rely on photosynthesis being active or on temperature-dependent metabolism, the residual keeps working in shaded areas and overnight. And because the compound is stable against ultraviolet light, the barrier persists between weekly doses rather than burning off each afternoon.

One important limitation: chlorine degrades quats. Free chlorine oxidizes quaternary ammonium compounds, so algaecide added into a heavily shocked pool is partly destroyed before it can establish a residual. Timing matters, and it's covered in the directions below.

Pro Tip: Don't add algaecide and shock at the same time. High free chlorine oxidizes quats, so dosing both together means paying for algaecide that gets destroyed before it does anything. Shock first, let the pool circulate, and add Back Up 2 once free chlorine has come back down into the normal 1–4 ppm range. The same logic applies in reverse after clearing an algae bloom — the shock does the killing, and the algaecide goes in afterward to hold the ground you just took. Owners who dump everything in on Saturday morning are quietly wasting a third of what they buy.

Directions for Use

Dosage Reference

  • Initial or start-up application: 6 fl oz per 10,000 gallons
  • Routine weekly maintenance: 1.5 fl oz per 10,000 gallons every 5 to 7 days
  • Heavy bather load or after prolonged rainfall: an additional maintenance dose
  • Vacation or unattended pool: 4 fl oz per 5,000 gallons for every week the pool will be unattended
  • Visible algae treatment: 13.5 fl oz per 10,000 gallons

Before You Start

  1. Confirm all pool equipment is working properly.
  2. Clean or backwash the filter following your equipment manufacturer's directions.
  3. Test total alkalinity, pH, and calcium hardness, and correct as needed.
  4. Adjust stabilizer to 30–50 ppm.
  5. Establish and maintain a proper sanitizer residual.

Start-Up Application

  1. With the pump running, add 6 fl oz per 10,000 gallons directly into the pool, distributing it around the perimeter.
  2. Allow the water to circulate to distribute the product.
  3. Begin weekly maintenance dosing 5 to 7 days later.

Routine Weekly Maintenance

  1. With the pump running, add 1.5 fl oz per 10,000 gallons directly into the pool.
  2. Repeat every 5 to 7 days throughout the swim season.
  3. Add an additional dose when bather load has been heavy or after prolonged rainfall — both dilute and consume the residual faster than normal.
  4. Apply after shocking rather than at the same time, once free chlorine has returned to 1–4 ppm.

Vacation and Unattended Pools

  1. Before leaving, balance the water and establish a proper sanitizer level.
  2. Add 4 fl oz per 5,000 gallons for every week the pool will be unattended.
  3. Run the pump on a timer while you're away — circulation is what carries the treatment to the places algae starts.
  4. Test and rebalance on return before anyone swims.

Treatment of Visible Algae

  1. Brush all pool surfaces thoroughly, using a brush compatible with your finish, and vacuum out loose debris.
  2. Shock the pool with an appropriate oxidizer and let it circulate per that product's label.
  3. With the pump running, add 13.5 fl oz per 10,000 gallons directly into the pool.
  4. Circulate continuously and wait 24 hours.
  5. After 24 hours, clean out the dead, settled algae by vacuuming or brushing to the filter.
  6. If algae is still present, repeat the dosage as necessary.
  7. Do not swim until free chlorine has returned to 1–4 ppm.
  8. Once clear, resume weekly preventative dosing to keep it from returning.

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: Expect foam, and dose accordingly. Quat algaecides lower the water's surface tension, so a fresh dose plus a waterfall, spillover, or set of jetted returns will produce a visible head of foam. It's temporary and harmless, and it clears as the product disperses. Two things make it a non-issue: add the algaecide in the evening so it has overnight circulation to disperse before anyone's looking at the pool, and stay at the label dose rather than rounding up. If your pool has heavy aeration year-round and foaming is a persistent annoyance, a non-foaming dual-action algaecide is the better fit for that installation.

Specifications
  • Brand: BioGuard
  • Product Type: Quaternary ammonium algaecide and algae preventative
  • Form: Liquid
  • Volume: 1 quart (32 fl oz)
  • Manufacturer Part Number: 23050BIO
  • Active Ingredient: Alkyl [50% C14, 40% C12, 10% C16] dimethyl benzyl ammonium chloride, 50%
  • Other Ingredients: 50%
  • Metal Content: None — contains no copper
  • Start-Up Dose: 6 fl oz per 10,000 gallons
  • Weekly Maintenance Dose: 1.5 fl oz per 10,000 gallons every 5–7 days
  • Vacation Dose: 4 fl oz per 5,000 gallons per week unattended
  • Visible Algae Dose: 13.5 fl oz per 10,000 gallons
  • Stabilizer Level Before Use: 30–50 ppm
  • Effect on pH: None
  • Staining: Non-staining when used as directed
  • Foaming: Temporary foaming is normal, especially with water features
  • UV Stability: Stable in sunlight; will not evaporate
  • Temperature Behavior: Activity increases as water temperature rises
  • Application Method: Add directly to the pool with the pump running
  • Suitable Surfaces: Plaster, gunite, vinyl liner, fiberglass, painted
  • Sanitizer Compatibility: Chlorine, bromine, salt generator, and mineral systems
  • Not A Substitute For: Sanitizer, shock, or brushing
  • Shipping Classification: DOT-regulated — ground shipping only
Compatibility

Pool Types and Surfaces

  • In-ground and above-ground pools
  • Plaster and gunite
  • Vinyl liner
  • Fiberglass
  • Painted surfaces
  • Sand, cartridge, and DE filtration

Sanitizer Programs

  • Chlorine pools — fully compatible; formulated to complement pool sanitizers
  • Bromine pools — fully compatible
  • Salt chlorine generator pools — fully compatible
  • Mineral system pools — fully compatible, and a good pairing since this product adds no metals of its own

Expect Some Foaming

Because of its surfactant properties, temporary foaming is normal after application, and it's more noticeable in pools with fountains, waterfalls, spillovers, attached spas, or jetted returns. It clears on its own. If it's persistent or you have a lot of aeration, a defoamer will knock it down immediately, or consider a non-foaming algaecide for that installation instead.

What It Does Not Do

  • Not a sanitizer. Provides no disinfection and maintains no sanitizer residual. Chlorine or bromine is still required.
  • Not a shock or oxidizer. Clearing an established bloom needs a shock treatment as well.
  • Not a substitute for brushing. Established algae has to be physically disturbed for any treatment to reach it.

Important Handling Cautions

  • Never mix with other chemicals. Add products separately, allowing circulation between additions.
  • Do not add alongside shock. High free chlorine degrades the active ingredient.
  • Spas and hot tubs — this is a pool product dosed per 10,000 gallons. Use a spa-specific algaecide.

Most products purchased from our online shop within the last 30 days are eligible for return. Please review our return policy to see the list of items that cannot be returned.

Some major items that are non-returnable:

  • Gift cards
  • Electronics
  • Pumps / Motors
  • Hot Tubs
  • Closeouts
  • Fireplaces
  • Electric Fireplaces
  • Massage Chairs
  • See return policy below for full list of non-returnables.

BioGuard® Brand FAQs

What is the BioGuard 3-Step Care System?

It's the brand's core program for traditional chlorine pools, and it reduces routine care to three jobs.Step 1, sanitize— SilkGuard Complete® tabs or sticks maintain a continuous chlorine residual that kills bacteria and controls algae between applications.Step 2, shock— Smart Shock® is applied weekly to oxidize the organic waste bathers leave behind, break apart chloramines, and restore clarity.Step 3, prevent— Algae Complete® stops algae before it establishes rather than fighting it after it blooms. The system works in pools of any size and surface type that circulate 10 to 24 hours per day.

What's the difference between BioGuard and SpaGuard?

They're sister brands from the same water-care company.BioGuard is the swimming pool line. SpaGuard is the spa and hot tub line.The split isn't marketing — pool dosing is calculated for tens of thousands of gallons at ambient temperature, while spa dosing is calculated for a few hundred gallons at 100°F. Pool packaging makes accurate spa measurement nearly impossible, and a pool-sized dose in a hot tub is a serious overdose. Match the product line to the vessel.

Which BioGuard program is right for my pool?

Equipment usually decides it. Pools running a standard chlorinator, feeder, or skimmer application belong on the3-Step Care System. Pools with a salt chlorine generator should be on thesalt pool programs— Mineral Springs® or SaltScapes® — which are formulated around the specific scale, balance, and cell-care demands of a generator. Owners who want no chlorine or bromine in the water at all use BioGuard'snon-chlorine biguanide program, which is a fully separate chemistry with its own sanitizer, oxidizer, and algaecide.

Can I mix BioGuard products with chemicals from other brands?

Basic balancers are chemically generic and generally interchangeable — alkalinity increaser is sodium bicarbonate no matter whose label is on the bucket. The real risk sits withsanitizer programs and specialty additives. Never introduce chlorine or bromine into a biguanide pool; the two chemistries destroy each other and produce cloudy water, gummy filter fouling, and a collapsed sanitizer residual. Also avoid stacking algaecides and clarifiers from different brands, since overlapping actives can cause foaming or staining. And regardless of brand, never combine two products in the same bucket, scoop, or feeder — always add them separately with circulation running between.

What is SilkGuard Technology?

SilkGuard® is a conditioning technology built into BioGuard's chlorinating tabs and sticks. It softens the feel of the water against skin and helps protect pool surfaces and equipment from scale formation, so the sanitizer is doing two jobs at once. SilkGuard Complete® products also carrySunShield® Technology, which shields free chlorine from ultraviolet breakdown. UV loss is the largest single drain on chlorine in an outdoor pool during summer, so protecting the residual directly reduces how much sanitizer you consume over a season.

Do BioGuard products work with salt chlorine generators?

Yes. A salt pool is still a chlorine pool — the generator simply produces the chlorine on site instead of you adding it from a bucket. Salt pools still need balancing, weekly oxidation, algae prevention, and scale protection, and they have one extra demand a standard pool doesn't: the generator cell itself accumulates scale and needs periodic cleaning. BioGuard's salt-specific programs are built around exactly those requirements.Do not skip testing on a salt pool— the automation controls chlorine production, not water balance.

About BioGuard®

BioGuard is a professional swimming pool care line built on a simple premise: pool chemicals work better as a program than as a shelf of unrelated purchases. Most water problems homeowners fight through the summer aren't caused by a bad product. They're caused by good products working against each other, applied out of sequence, in water whose balance was never corrected in the first place. BioGuard's entire approach is organized around fixing that — matched products, a defined order of operations, and a diagnostic process behind the recommendation.

The brand sits under the KIK Consumer Products umbrella alongside its spa counterpart, SpaGuard, and it covers the full range of pool water care: sanitizers, shocks, algaecides, balancers, water enhancers, surface cleaners and problem solvers, salt pool products, and off-season closing chemistry.

Three Programs, One Philosophy

  • Traditional Chlorine — the 3-Step Care System — Sanitize, shock, prevent. SilkGuard Complete® tabs and sticks handle daily sanitation, Smart Shock® handles weekly oxidation and clarity, and Algae Complete® handles algae prevention. Suitable for pools of any size and surface type running 10 to 24 hours of circulation per day.
  • Salt Pools — Purpose-built chemistry for pools with a chlorine generator, including the Mineral Springs® and SaltScapes® programs. Salt pools still generate chlorine, and they still need balancing, scale protection, and cell care — these products are formulated for that specific equipment set.
  • Non-Chlorine Pools — A complete biguanide-based program for owners who want no chlorine and no bromine in the water at all, with its own dedicated sanitizer, oxidizer, and algaecide.

Formulation Technologies

Two proprietary technologies show up across the chlorine line and explain a lot of the brand's reputation. SilkGuard® Technology conditions the water so it feels noticeably softer against skin while also helping protect pool surfaces and equipment from scale. SunShield® Technology protects free chlorine from ultraviolet breakdown, which is the single largest source of chlorine loss in an outdoor pool during summer — sanitizer that survives the afternoon is sanitizer you don't have to replace.

Diagnosis, Not Guesswork

BioGuard is sold through trained specialty dealers rather than mass-market channels, and the brand backs that network with the ALEX® water analysis system. ALEX reads a full water sample — sanitizer, pH, total alkalinity, calcium hardness, cyanuric acid, metals, and more — and returns a sequenced correction plan rather than a generic product suggestion. That distinction matters more than it sounds. Cloudy water has at least six common causes, and the fix for a filtration problem is nothing like the fix for a high-pH problem or a phosphate problem. Testing tells you which one you actually have.