Three chemistries, and one of them foams

The best pool algaecide for 2026

Algaecide is a preventative rather than a cure, and the chemistry printed on the back decides which of three quite different products you have. Quaternary ammonium compounds — "quats" — are the cheapest and the most common; they work, they are degraded by chlorine, and above a certain dose they foam, which is the complaint behind most one-star reviews on this shelf. Polyquats (polymeric quaternary ammonium) cost more, do not foam, and tolerate chlorine better. Copper-based algaecides are the most effective against stubborn black and mustard algae, and they carry the one risk the others do not: copper stains a liner and turns blond hair green if the water chemistry lets it come out of solution. The number to compare is the concentration of active — anywhere from 5 % to 60 % on this shelf — together with the dose per cubic metre, because a 60 % concentrate dosed at 3 ml/m³ and a 10 % product dosed at 20 ml/m³ can cost the same per season from very different bottle prices. Then whether the product is stated chlorine-compatible, which matters for anything meant to sit in the water between treatments, and whether it is a maintenance or a shock dose — the two differ by a factor of three to five in almost every range. We compare active chemistry, concentration, dose per cubic metre, foaming, copper content and chlorine compatibility.

These parts, one figure beside another

1. 

   Meinpool24.de Algizid 5 l

   Five litres of foam-free liquid algaecide stated to prevent all algae types, single-celled or multi-celled, and to be usable with most disinfectants and pool chemicals.

   Active chemistry

   Not published

   Concentration

   Not published

   Dose per cubic metre

   Not published

   Foaming

   Foam-free, stated

   Copper content

   Not published

   Chlorine compatibility

   Stated usable with most disinfectants and pool chemicals. Registration number N-111919

   Amazon reference

   B0BZL67TL4 (one reference across 1 Amazon marketplace)

   EAN

   4262387170561

   • States compatibility with most disinfectants and pool chemicals, which only two listings here do
   • Foam-free, stated — one of three on this shelf
   • No dose published, where four algaecides in this family publish one

   Best for: A pool already running a chlorine or oxygen routine, where compatibility is the question

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2. 

   Höfer Chemie Algizid 5 L

   Five litres with a published dose adjusted for the weather — 70 to 140 ml per 10 m³ at first use, 25 to 50 ml weekly — and a method for treating the walls before the pool is filled.

   Active chemistry

   Not published

   Concentration

   Not published

   Dose per cubic metre

   70–140 ml per 10 m³ at first use depending on the weather, then 25–50 ml per 10 m³ weekly. On first filling, walls and floor can be rubbed with algaecide and the pool filled an hour later

   Foaming

   Foam-free, stated

   Copper content

   Not published

   Chlorine compatibility

   Not published. Stated a high-quality biocide for pool use. BAuA registration number N-42291

   Amazon reference

   B005DYG6Q0 (one reference across 3 Amazon marketplaces)

   EAN

   4250463101707

   • Publishes a dose that varies with the weather rather than a single number
   • Publishes a pre-fill method: rub the walls, wait an hour, then fill
   • No chemistry and no concentration, so the dose cannot be compared with any rival

   Best for: A pool being filled for the season, where the walls can be treated before the water goes in

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3. 

   AGUALEVE Algizid 1 l

   A one-litre algaecide — the smallest on this shelf — stated to disinfect without chlorine and to clarify as well, with bathing possible immediately after dosing.

   Active chemistry

   Not published

   Concentration

   Not published

   Dose per cubic metre

   Not published — the listing directs the reader to the label for the quantity

   Foaming

   Not published

   Copper content

   Not published

   Chlorine compatibility

   Not published as compatibility. Stated to have a disinfecting action without chlorine and an additional clarifying effect. BAuA registration number N-103312

   Amazon reference

   B09RG96LBZ (one reference across 1 Amazon marketplace)

   EAN

   4260746790221

   • A 1 l bottle, which suits a hot tub or a small pool that would not use five litres
   • States that bathing is possible immediately after dosing
   • No dose published — the listing explicitly refers the reader to the label

   Best for: A hot tub or small pool where a litre is a season and the label supplies the dose

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4. 

   well2wellness Algenvernichter Extra 5 L

   A highly concentrated non-metallic algaecide dosed at 60 to 90 ml per 38 000 litres — the lowest published dose on this shelf by a wide margin — stated foam-free and pH-neutral.

   Active chemistry

   Not published as a compound. Stated non-metallic and made under the supervision of organic chemistry experts

   Concentration

   No figure published. Stated highly concentrated

   Dose per cubic metre

   60–90 ml per 38 000 l — about 16 to 24 ml per 10 m³ — waiting 15 minutes for it to act, weekly or every 10 days, increased in storms or higher temperatures. The lowest published dose in this family

   Foaming

   Completely foam-free, stated, and attributed to the pH-neutral formulation

   Copper content

   Free of heavy metals, stated — explicitly a non-metallic algaecide. One of two such statements in this family

   Chlorine compatibility

   Not published. Stated to act as a disinfectant and remove cloudiness. BAuA number N-54471

   Amazon reference

   B008XJMPKS (one reference across 3 Amazon marketplaces)

   EAN

   4260284076122

   • The only listing here to name itself a non-metallic algaecide rather than only claiming heavy-metal freedom
   • The lowest published dose on this shelf — a fifth of the highest, per cubic metre
   • No compound named and no concentration figure behind the highly concentrated claim

   Best for: A larger pool where a concentrated non-metallic product is wanted and copper is to be avoided

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5. 

   PoolLöwe Algenvernichter Klareffekt 2.0

   An algaecide with a clarifying effect whose formula is stated to have been developed specifically for small pools — the only such statement on this shelf.

   Active chemistry

   Not published. Referred to as a ClearProtect formula

   Concentration

   Not published

   Dose per cubic metre

   Not published

   Foaming

   Not published

   Copper content

   Not published

   Chlorine compatibility

   Not published. Stated to prevent algae, germs and fungi forming. BAuA notification number N-110516

   Amazon reference

   B0C6FHMJ71 (one reference across 1 Amazon marketplace)

   EAN

   4260614920620

   • The only listing here whose formula is stated to be developed for small pools
   • Addresses the pool that has already turned as well as prevention
   • No dose, no chemistry, no concentration, no foam or copper statement

   Best for: A small above-ground pool treated preventively, where the label supplies the dose

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6. 

   PoolsBest Algenverhüter extra 5 L

   The highest published dose on this shelf — 300 ml per 10 m³ at first use, then 100 ml weekly — in a chlorine-free, heavy-metal-free formulation that does not foam in a counter-current unit.

   Active chemistry

   Not published. Stated free of chlorine and of heavy metals

   Concentration

   Not published. Stated highly dosed and highly concentrated

   Dose per cubic metre

   300 ml per 10 m³ at first addition, then 100 ml per 10 m³ weekly — the highest published dose in this family

   Foaming

   Does not foam when cleaning, stated, and therefore suitable for a counter-current swim unit

   Copper content

   Free of heavy metals, stated. One of two such statements in this family

   Chlorine compatibility

   Not published as compatibility. The product itself is stated chlorine-free

   Amazon reference

   B0036HI0NS (one reference across 1 Amazon marketplace)

   EAN

   4039117871490

   • The only listing here to explain what foaming would actually spoil — a counter-current swim unit
   • States freedom from both chlorine and heavy metals
   • At 300 ml per 10 m³ the initial dose is the highest here, so five litres goes less far than it looks

   Best for: A pool with a counter-current unit, where a foaming algaecide is not an option

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7. 

   TerraUno Algizid 5 L

   The fullest dosing instruction on this shelf: 50–100 ml per 10 m³ to start, then 20 ml weekly indoors or 40 ml outdoors, up to 600 ml after a shock treatment for heavy infestation.

   Active chemistry

   Not published

   Concentration

   Not published. Stated highly concentrated

   Dose per cubic metre

   pH set to 7.0–7.4 first. Initial 50–100 ml per 10 m³; weekly 20 ml per 10 m³ indoors or 40 ml per 10 m³ outdoors, added at the inlet nozzles; up to 600 ml per 10 m³ after a shock treatment in heavy infestation. Preventively, the pool wall can be treated undiluted with a sponge before filling

   Foaming

   Not published

   Copper content

   Not published

   Chlorine compatibility

   Not published as compatibility, though the heavy-infestation dose is stated to follow a shock treatment. BAuA registration N-117549

   Amazon reference

   B0FDBKDHJ3 (one reference across 1 Amazon marketplace)

   EAN

   9008748015240

   • The only listing in this family to publish different weekly doses for indoor and outdoor pools
   • Publishes a heavy-infestation figure and states it comes after a shock treatment, not instead of one
   • No chemistry, no concentration, no foam statement, no copper statement

   Best for: An outdoor pool treated to a published routine, and a pool recovering from a heavy infestation

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