Algaecide for an above-ground pool
Updated: 16.10.2026
A 10 ft or 15 ft frame pool in a UK garden goes green after sun, or it sits under a cover from autumn to spring. An algaecide for an above-ground pool only helps when the dose matches the litres you have. The [algae killer pool comparison](/hub/pool-care/algae-killer-pool) lists the six cards and the prices from 15 October 2026. This page stays with Intex, Bestway-type and other frame or paddling pools. Amazon links are affiliate links. A qualifying purchase can earn a commission at no extra cost to you. Products Compared did not measure your pool.
A 10 ft or 15 ft frame pool in a UK garden goes green after sun, or it sits under a cover from autumn to spring. An algaecide for an above-ground pool only helps when the dose matches the litres you have.
A 10 ft or 15 ft frame pool in a UK garden goes green after sun, or it sits under a cover from autumn to spring. An algaecide for an above-ground pool only helps when the dose matches the litres you have. The algae killer pool comparison lists the six cards and the prices from 15 October 2026. This page stays with Intex, Bestway-type and other frame or paddling pools. Amazon links are affiliate links. A qualifying purchase can earn a commission at no extra cost to you. Products Compared did not measure your pool.
Our top picks
| Badge | Product | Vessels named | Treat-volume claim | Pack | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  KLEEN POOL Kleen Pool 1 litre algaecide | Swimming pools | 28,000 litres | 1 litre | 8.5 | about £17.95 | View offer |
| Alternative |  KLEEN POOL Kleen Pool long-life algaecide | Swimming pools | Up to 28,000 litres | 1 count; litres not stated | 6.6 | about £17.95 | View offer |
| Best value |  Clearwater Clearwater 1 litre algaecide | Hot tub, spa, paddling pool, above-ground | n/a | 1 litre | 8.2 | about £9.55 | View offer |
On this page
Sun and a short pump run are the usual cause
Outdoor pools grow algae because sunlight reaches the water. PWTAG’s technical note says so, and adds that phosphates in some mains water can feed the growth. For a garden pool the public point is enough: sun, a residual that is not really working, and poor turnover.
A test strip can look fine beside green water if the pH is high or the pump barely runs. For managed pools, each 0.5 rise in pH roughly doubles the chlorine required. HSG179 does not set the millilitres for a patio frame pool. A title that says 28,000 litres will not fix a pump you never switch on. Brush, circulate, then dose is on the how to use page. This page is about how small the pool is next to the number on the bottle.
A frame pool is a small fraction of 28,000 litres
Kleen Pool’s 1 litre title, at £17.95, says 28,000 litres. That is the top of the claim, not a 10 ft or 12 ft pool. Pool & Spa Centre’s table runs 250 ml for 6,820 litres, 500 ml for 14,100 litres, and 1 litre for 28,200 litres. The 250 ml row is the frame-pool row. Amazon says 28,000 where the table says 28,200. If the bottle disagrees, the bottle wins.
On the 585-review card, half a bottle in a 15 ft Intex is an autumn story, and a stated 10,000 litre pool cleared after a shock the day before with the filter on. Another review says 250 ml in a 12 ft frame pool. A 9 ft paddling pool is smaller again. Half a bottle is one close-down, not a formula.
Closing for winter is a different job from a green Monday
Kleen Pool reviews often describe an autumn dose and a cover, including half a bottle in a 15 ft Intex. That pattern is common in the UK sample, and it is not a promise through a hot uncovered August. Then open the pool, test it, and clean what has settled.
A green Monday is the other job. Brush, sort the chlorine if that is your sanitiser, and circulate. Clearwater reviews that end well mention the filter. Others stayed green. A bloom already in the water will not wait for a cover. Clearwater names a hot tub. Kleen Pool only has the question. Keep a 28,000 litre dose out of a spa.
Empty it when the water is a swamp you will not filter
A bottle has a limit, and this page will not fake a litre cutoff. If you cannot run a pump, or the water is past a cartridge filter, emptying can be the cleaner decision. That judgement is set out in when to empty a green pool. It is not an order to dump every green Intex, and not a diameter where treatment stops.
The rainwater Bestway review still reported a result. The refill that stayed green is the other outcome. Read your own filter. Match the dose to the water you have. A 15 ft line is one Intex, the 10,000 litre account had been shocked the day before, and a 9 ft paddling pool is smaller again. These cards state no swim-wait, so the bottle is the only source for when anyone gets back in. Mustard film, and a Clearwater starter kit under another ASIN, sit outside this page.
Common questions
How do I treat a green Intex pool?
Brush, check the sanitiser if you use one, run the pump, and add only the label dose for the litres you have. A 15 ft Intex in the Kleen Pool reviews is often a winter half-bottle, which is one pool, not a chart. A green pool with the pump off will not clear because the bottle cost £17.95. The order of work is on the how-to page. The scale is the point here.
Is half a bottle right for a 15 ft pool?
Some UK reviewers report half a bottle for a 15 ft Intex at closing, on the Kleen Pool litre. That is not a manufacturer chart, and not automatic for 12 ft or 10 ft. The trade table’s smaller row is 250 ml for 6,820 litres, and a 12 ft review describes 250 ml. Work out your water, then follow the label if it disagrees with the table.
Can I leave the pool covered all winter with one dose?
Kleen Pool reviews often describe an autumn dose, a cover, and acceptable water at opening, including half a bottle in a 15 ft Intex. The title says six months and 28,000 litres. That plan weakens if the cover leaks, the dose was for the wrong volume, or you never circulate at opening. A hot August with no cover is a different season. Uncover, test, and clean settled debris.
Is a paddling pool the same dose as a frame pool?
No. A 9 ft paddling pool in the Kleen Pool reviews is smaller than a 12 ft frame pool or a 15 ft Intex. Clearwater names paddling pools separately from larger above-ground pools, and still prints no millilitres. Use the label for the litres in that pool. A whole bottle aimed at 28,000 litres is the wrong habit in a paddling pool and in most frame pools.
Which card actually names above-ground pools?
Clearwater’s bullets do, on the 1 litre card at £9.55: larger above-ground pools, plus paddling pools, hot tubs and spas. The 6 litre card at £47.99 repeats those bullets, and its written reviews match the 1 litre file. Kleen Pool’s titles say swimming pools up to about 28,000 litres. Intex and frame pools turn up in UK reviews, which is use, not a bullet. Take the dose from the bottle either way.
Related pages
Sources
Public UK sources and the stored amazon.co.uk listings, from the research digest. Shelf prices and star lines are the UK figures in the display file, snapshot 15 October 2026.
- HSE: biocidal product types, including pool algaecides (retrieved 15 October 2026)
- Retained BPR Annex V, product type 2 (retrieved 15 October 2026)
- HSE: UK authorised biocidal products (retrieved 15 October 2026)
- HSE: swimming pools and HSG179 (retrieved 15 October 2026)
- PWTAG: typical pool problems (retrieved 15 October 2026)
- Pool & Spa Centre: Kleen Pool dose table (retrieved 15 October 2026)
- GTS Shop: Clearwater CH0006 active (retrieved 15 October 2026)