Makes fine particles big enough for a filter that cannot see them

The best pool flocculant for 2026

A flocculant does something no filter can do: it makes suspended particles clump until they are large enough for a filter to catch or heavy enough to fall. It is the tool for water that is clear-but-hazy — fine clay, dead algae, sun cream — where every reading is correct and the pool still looks like milk. The first thing to establish is which of two products you are buying, because they are used in opposite ways. A clarifier is a mild polymer dosed continuously; particles clump slightly, the filter catches them, and the pool keeps running normally. A true flocculant — usually aluminium sulphate — is dosed once, the pump is stopped, and the floc sinks to the floor over several hours to be vacuumed to waste rather than filtered. Vacuuming a floc through the filter puts it straight back into the pool, which is the single most common mistake on this shelf. The second point is the filter: flocculants belong in sand filters, and cartridge filters clog on them almost immediately — several makers state this and several do not. Then the form: liquid, granules, or the cartridge-shaped "floc socks" that sit in the skimmer, which are a slow clarifier despite the name. And the dose per cubic metre, which is the only comparable price. We compare form, active chemistry, dose per cubic metre, contact time, filter compatibility and whether waste vacuuming is required.

These parts, one figure beside another

1. 

   Meinpool24.de Flockkartuschen 1 kg

   Flocculant cartridges publishing their chemistry down to the CAS number — aluminium sulphate hexadecahydrate — dosed at one cartridge per 20 to 40 m³, lasting one to two weeks.

   Form

   Cartridge, 1 kg pack

   Active chemistry

   Aluminium sulphate hexadecahydrate, CAS 16828-11-8 — the only CAS number published in this catalogue

   Dose per cubic metre

   One cartridge for 20 m³ to 40 m³. Depending on soiling, one cartridge lasts 1 to 2 weeks. The pH should be 7.0–7.4 before adding

   Contact time

   No figure published. The flocculant is released continuously into the water, stated

   Filter compatibility

   Suitable for systems with sand filters and with filter glass, stated

   Waste vacuuming required

   Not stated as vacuuming. The flocs are held by the running filter and removed on backwashing

   Amazon reference

   B093MQK3S7 (one reference across 1 Amazon marketplace)

   EAN

   4260289330762

   • Publishes the CAS number of its active substance — the only one in this catalogue
   • Publishes both a volume range and a duration for one cartridge
   • The volume range is a doubling — 20 to 40 m³ — without a criterion for choosing within it

   Best for: A sand or glass filter, dosed through the skimmer and cleared by backwashing

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2. 

   Veddelholzer Poolklar 0,5 L

   A half-litre liquid clarifier dosed at 30 ml per 10 m³ weekly with the pump run for eight hours afterwards, stated suitable for all filter types including cartridges and filter balls.

   Form

   Liquid, 0.5 L — the smallest pack in this family

   Active chemistry

   Not published. Stated a highly concentrated formula dissolving quickly without residue

   Dose per cubic metre

   30 ml per 10 m³, once a week, added directly to the pool

   Contact time

   Run the circulation pump for the next 8 hours after adding, stated

   Filter compatibility

   All filter types and systems — glass, sand, filter balls or cartridges. Fresh and salt water alike, and all pool materials: GRP, liner, concrete

   Waste vacuuming required

   Not published. Stated to improve the pump’s filtration performance

   Amazon reference

   B0BZJ63CNB (one reference across 5 Amazon marketplaces)

   EAN

   8720828441367

   • The only listing here to state compatibility with filter balls and cartridges as well as sand and glass
   • Publishes both a dose and a circulation time
   • No chemistry named, where four listings in this family name theirs

   Best for: A cartridge filter or a filter-ball system, where most of this shelf does not belong

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3. 

   Cristal Klareffekt Trübungsentferner

   The lowest published dose on this shelf — 10 ml per 10 m³ weekly — with the pH at 7.0 to 7.4 and the filter running at least eight hours, in a formulation stated to require no hazard labelling.

   Form

   Liquid

   Active chemistry

   Not published. Stated a label-free formulation developed and made in Germany, residue-free

   Dose per cubic metre

   10 ml per 10 m³, once a week. Best effect at a pH between 7.0 and 7.4. The lowest published dose in this family

   Contact time

   The filter system should run at least 8 hours after dosing, stated

   Filter compatibility

   Stated to work independently of the filter system, improving the performance of sand AND cartridge filters. Suitable for fresh and salt water and for liner, concrete and GRP

   Waste vacuuming required

   Not published. Stated residue-free

   Amazon reference

   B001UACI86 (one reference across 4 Amazon marketplaces)

   EAN

   4002369953269

   • The lowest published dose here — a third of the next liquid on this shelf
   • Names sand and cartridge filters explicitly as both being improved
   • No chemistry named, where four listings in this family name theirs

   Best for: A pool of any filter type, dosed weekly at a low rate with an overnight run

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4. 

   Höfer Chemie BAYZID Flockungsmittel 5 L

   Five litres of liquid flocculant made on an aluminium sulphate basis to DIN 19600 — the only standard cited on this shelf — stated for sand filter systems.

   Form

   Liquid, 5 L — joint largest in this family

   Active chemistry

   Aluminium sulphate basis, manufactured to DIN 19600 — the only standard cited in this family

   Dose per cubic metre

   Not published

   Contact time

   Not published

   Filter compatibility

   Stated best suited to the use of sand filter systems, with filter performance noticeably increased. Cartridge filters are not mentioned

   Waste vacuuming required

   Not published. Stated to eliminate dead algae and dissolved lime residues

   Amazon reference

   B005DYSR62 (one reference across 4 Amazon marketplaces)

   EAN

   4250463101851

   • The only listing in this family to cite a standard for its active substance — DIN 19600
   • Names what it removes: dead algae and dissolved lime residues
   • No dose published, on a liquid poured into water

   Best for: A sand filter installation where the standard behind the chemistry is the deciding factor

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5. 

   KLEP Flockungsmittel 5 L

   Five litres of polyaluminium chloride at a published 10 to 20 per cent — the only concentration on this shelf — dosed pre-diluted into the skimmer with a backwash afterwards.

   Form

   Liquid, 5 L, pale yellow, specific gravity 1.10–1.20

   Active chemistry

   Polyaluminium chloride 10–20 % — the only active concentration published in this family. pH of the product as supplied 2.0–3.0

   Dose per cubic metre

   Removal: 15 g pre-diluted into the skimmer per m³ of water, followed by a backwash. Prevention: 10 g pre-diluted into the skimmer per 10 m³ of water

   Contact time

   Not published. A backwash is to be carried out after the removal dose

   Filter compatibility

   Not published as a filter list. The instruction to backwash implies a backwashable filter

   Waste vacuuming required

   Not published. A backwash is stated after the removal dose

   Amazon reference

   B06Y67GKKK (one reference across 6 Amazon marketplaces)

   EAN

   8018544110798

   • The only listing here to publish an active concentration — 10 to 20 per cent
   • Publishes the product’s own pH and specific gravity
   • The German text is a rough machine translation and parts of it are unreadable

   Best for: A backwashable filter where a concentrated polyaluminium product is wanted

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6. 

   Bayrol Superflock Plus 1 kg

   Lanthanum-based cartridges that remove phosphates and metals as well as cloudiness, dosed one per 50 m³ after backwashing — and stated only for sand filters and filter glass.

   Form

   Cartridge, 1 kg pack, placed in the skimmer after backwashing

   Active chemistry

   An exclusive formula with lanthanum — the only lanthanum product in this family

   Dose per cubic metre

   One cartridge per 50 m³ weekly, placed in the skimmer after backwashing. Set the pH to 7.0–7.4 before adding

   Contact time

   Not published. The cartridge works continuously

   Filter compatibility

   ONLY suitable for sand filters and filter glass. For cartridge filters the maker names a different product — BAYROL Superklar. The only explicit exclusion in this family

   Waste vacuuming required

   Not published. The flocs are held by the sand or glass bed

   Amazon reference

   B003F04UFI (one reference across 5 Amazon marketplaces)

   EAN

   0638414896980

   • The only listing here to publish an explicit filter exclusion and name the alternative product
   • Removes phosphates — algae nutrient — and metals such as iron and copper, stated
   • Not for cartridge filters, by the maker’s own statement

   Best for: A sand or glass filter on a large pool, where phosphate is feeding the algae

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7. 

   AGUALEVE Flockmittel Kartuschen 8 × 125 g

   A pack of eight 125 g flocculant cartridges for sand filters, filter balls and glass filters. Every one of its five bullets describes a different product: an all-in-one fountain care liquid, with its own separate registration number.

   Form

   Cartridge, 8 × 125 g, published in the title — the only per-cartridge weight in this family

   Active chemistry

   Not published. The bullets describe a different product and name no flocculant chemistry

   Dose per cubic metre

   Not published for this product. The bullets publish 50 ml per 1 000 litres weekly for an all-in-one FOUNTAIN care liquid, which is not what the title sells

   Contact time

   Not published

   Filter compatibility

   Sand filters, filter balls and glass filters, published in the title

   Waste vacuuming required

   Not published. The bullets carry BAuA registration N-113428, which is the fountain product’s number

   Amazon reference

   B0BRQN4WW4 (one reference across 5 Amazon marketplaces)

   EAN

   4260746791129

   • The only listing in this family to publish a per-cartridge weight — 125 g
   • Names three filter media in the title: sand, filter balls and glass
   • Every bullet describes an all-in-one fountain care product, not a pool flocculant

   Best for: A sand, glass or filter-ball system, once the seller has confirmed what is actually in the pack

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