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Best clay granules for houseplants UK

Updated: October 2026

You want one bag you can buy, not a type lecture. The best clay granules for houseplants UK in this amazon.co.uk set depend on the job: loose pebbles for topping and crocking, pumice for a printed 2–5 mm grade, or a compost that only names Seramis. There is no branded Seramis indoor-granule listing in this comparison. The full grid is the [Seramis granules comparison](/hub/fertiliser-soil-and-bark-mulch/seramis-granules). Type, litres and peat-free wording stay on the [Seramis granules buying guide](/hub/fertiliser-soil-and-bark-mulch/seramis-granules/sub/seramis-granules-buying-guide).

You want one bag you can buy, not a type lecture.

Our top picks

COMPO COMPO pumice granules 6 L

Best overall

COMPO COMPO pumice granules 6 L
9.4/10about £29.78
View offer
Westland Westland orchid mix 4 L

Best value

Westland Westland orchid mix 4 L
9.2/10about £7.29
View offer
Westland Westland Hydroleca 10 L

Rank 3

Westland Westland Hydroleca 10 L
9.2/10about £13.55
View offer
On this page
  1. 1.If you want loose clay or LECA
  2. 2.If you want pumice
  3. 3.If you want a named mix
  4. 4.Shared reviews and what the labels mean

If you want loose clay or LECA

Westland Hydroleca 10 L (B07LB7DPLY) is the clay bag: about £13.55, 4.6 from 569, first 50 reviews from the United Kingdom. Use it as a top, a crock, a mix or a humidity tray. Reviewers capped orchids and said tiny flies dropped. Skip it for a closed-pot Seramis store. Ball size varies, and the unit count is 1 against a 10 litre title. Invigortex 1 L (B0FVY94JHL) is the trial at about £7.49, 4.2 from 13. Blend 20–50 per cent or use a top layer, then rinse and reuse. Skip it when you are filling many pots. Why the top dries while the base stays wet is on Seramis granules or LECA.

If you want pumice

COMPO 6 L (B0CJCCFL4R) is the only pumice row: about £29.78, about £5 a litre, printed 2–5 mm, volume agreed. Use it neat, at up to 25 per cent, or as a 2–3 cm top. Colour is the wet or dry cue. The line is 4.7 from 319, and the first 50 reviews are almost all from other Amazon marketplaces. Bags split between finer than expected and large pieces. Skip it for cheap volume, a deep UK review file, or a closed-pot Seramis kit. The 96 per cent less CO2 line is a manufacturer claim.
COMPO COMPO pumice granules 6 L

Testsieger

COMPO COMPO pumice granules 6 L
9.4/10about £29.78
View offer

If you want a named mix

Westland orchid 4 L (B0765ZQJYH) is the lowest bag price and the deepest mix file: about £7.29, 4.6 from 8,049, first 50 reviews from the United Kingdom. Pine bark plus Seramis, sold for a 14 cm pot. Reviews mention new leaves, density, one Miracle-Gro substitution, and an older peat note. The listing does not print peat-free. Skip it as houseplant compost. UK GROW cactus 4 L (B0B3LN79XP) is about £10.29 and peat-free, sharing 4.6 from 166 with the 50 L (B0B3L81NRN) at about £34.99 and 20 kg. Skip 50 L for three pots. Topline citrus 2 x 10 L (B0GKG6YD6Q) is about £20.00, 4.6 from 14, unit count 6,000 g. UK GROW houseplant 9, 20 and 40 L are about £10.79, £14.99 and £23.99, one shared 3.5 from 51, unmarked sacks, 40 L at 16 kg. Cachepots sit on Seramis granules for houseplants.

Shared reviews and what the labels mean

Stars here are listing lines, not laboratory ranks. The houseplant sizes share one 3.5 from 51. The cactus sizes share one 4.6 from 166, and short-fill notes in that pool often name 2 or 3 litre packs, not the 50 litre sack. Hydroleca is the top pick as the deepest loose-granule file that is still clay. Westland orchid is the best value as the lowest bag price plus the deepest review file. Those labels do not make Hydroleca a closed-pot Seramis system, and they do not make the orchid mix a houseplant compost.

Common questions

Which bag is the actual clay granule in this set?
Westland Hydroleca 10 L. It is ceramic clay pebbles with a dense skin, sold for topping, crocking, mixing and humidity. Invigortex 1 L is LECA grit in a trial pack. COMPO is pumice. The other rows are composts that name Seramis. There is no branded Seramis indoor-granule listing in this comparison.
Which mix has the deepest UK reviews?
Westland orchid mix 4 L, at 4.6 from 8,049, with the first 50 reviews from the United Kingdom. That depth is about an orchid bark mix, not about Hydroleca or UK GROW. Do not copy those stars onto another row.
Is the 20 L houseplant mix a good buy at 75p a litre?
Only if you accept a 3.5 from 51 shared with the 9 L and 40 L bags, and reviews that talk as much about unmarked sacks as about the mix. Per litre looks cheap. Review risk is not the same as price. If you need a labelled sack, skip the line.
Who should buy the 1 L LECA grit?
Someone who wants to test grit in one or two pots, or as a top dressing, before buying volume. It is about £7.49 for 1 litre. Hydroleca 10 L at about £13.55 is the cheaper pebble bag per litre. Skip the grit if you are filling many pots.
Is COMPO pumice worth about £5 a litre?
It is the bag to buy if you wanted a named 2–5 mm pumice and will use it neat, at up to 25 per cent in a mix, or as a 2–3 cm top. It is the wrong bag for cheap volume, and the first 50 reviews are not UK texts. It is not a Seramis closed-pot kit.
Should I buy the 50 L cactus bag if I have three pots?
No. The 4 L cactus bag is the 14 cm pot size in this set. The 50 L is about £34.99 and 20 kg, for many pots. Both sizes share one 4.6 from 166. Three pots do not need 50 litres.
Why do three houseplant sizes share one star rating?
Amazon grouped the 9 L, 20 L and 40 L UK GROW houseplant listings on one 3.5 from 51 line. The reviews match across those listings. You are choosing a bag size of one mix, not three separately tested products.

Related pages

How to use Seramis granules

Seramis granules

Seramis granules buying guide: type, litres and peat

Clay granules for houseplants: caps, gnats and trays

Seramis vs LECA: open-pore clay or expanded pebbles

Sources

Public UK and maker sources from the research digest, used for this page in October 2026. Prices, stars and review counts are from the ten amazon.co.uk listings in the stored pages. A gnat, watering or CO2 line is the manufacturer's claim. Peat-free means those words on that listing. This is not a laboratory test.

  1. Seramis, granules and hydroponics (retrieved October 2026)
  2. Seramis, common questions (retrieved October 2026)
  3. Seramis 15 L granules on amazon.co.uk (retrieved October 2026)
  4. Westland Hydroleca clay granules (retrieved October 2026)
  5. Westland orchid potting mix (retrieved October 2026)
  6. RHS, growing media for houseplants (retrieved October 2026)
  7. RHS, peat-free compost (retrieved October 2026)
  8. Written answer on peat sales, 19 March 2026 (retrieved October 2026)