Seramis granules buying guide

Updated: October 2026

You typed Seramis into amazon.co.uk and the first page mixed red-brown clay, Hydroleca pebbles, a 6 litre pumice sack and a 4 litre orchid compost. The bag price will not sort that.

You typed Seramis into amazon.co.uk and the first page mixed red-brown clay, Hydroleca pebbles, a 6 litre pumice sack and a 4 litre orchid compost. The bag price will not sort that. This Seramis granules buying guide puts the checks in order: name the type, name the job, then check whether the litres on the title agree with the unit count, and whether the bag says peat-free. The Seramis granules comparison keeps the ten-pack grid. Which pack to buy, and which to skip, is on best Seramis granules.

Our top picks

Badge	Product	Type	Volume agrees	Main job	Note	Price	Offer
Best overall	COMPO COMPO pumice granules 6 L	Pumice	Yes	Substrate, mix or top	9.4	about £29.78	View offer
Best value	Westland Westland orchid mix 4 L	Orchid mix	Yes	Orchid potting mix	9.2	about £7.29	View offer
	Westland Westland Hydroleca 10 L	Expanded clay	No	Topping, crocking, tray	9.2	about £13.55	View offer

Best overall

COMPO COMPO pumice granules 6 L

9.4/10about £29.78

View offer

Best value

Westland Westland orchid mix 4 L

9.2/10about £7.29

View offer

Rank 3

Westland Westland Hydroleca 10 L

9.2/10about £13.55

View offer

On this page

1.The four things sold as Seramis granules
2.Litres, unit-count clashes and price per litre
3.Peat-free, dust and what the bag must say
4.What this page leaves to the next click

The four things sold as Seramis granules

Four families share this search. Open-pore fired clay stores water in the particle, in a watertight pot, soil ball left on. Expanded clay here is Hydroleca or 1 litre LECA grit: dense skin, honeycomb core, for a top, crocking, a mix or a humidity tray. Pumice is volcanic glass. COMPO’s 6 litre bag is 2–5 mm, used neat, at up to 25 per cent, or as a 2–3 cm top. The fourth family only names Seramis inside compost: orchid with pine bark, houseplant with perlite, cactus with grit and sand, citrus. A 4 litre orchid mix is not a 10 litre Hydroleca bag. Shop packs at 2.5, 7.5, 15 and 25 litres are not rows here. Pores are on Seramis granules or LECA.

Litres, unit-count clashes and price per litre

Stored prices run from about £7.29 (orchid 4 L) and about £7.49 (Invigortex 1 L) through about £13.55 (Hydroleca 10 L) and about £14.99 (houseplant 20 L) to about £29.78 (COMPO 6 L) and about £34.99 (cactus 50 L). Per litre, as a rule of thumb: about 75p for the 20 L mix, £1.36 for Hydroleca, £1.82 for the orchid mix, £5 for pumice and £7.50 for the 1 L grit. Volume agrees only when title, volume field and unit count match. Orchid 4 L and COMPO 6 L do. Hydroleca says 10 L and the unit count is 1. Houseplant 9, 20 and 40 L clash the same way. Topline says 2 x 10 L with a unit count of 6,000 g against 6 kg. A short or unmarked sack is a Consumer Rights Act 2015 point. Houseplant sizes share 3.5 from 51. Cactus sizes share 4.6 from 166.

Testsieger

COMPO COMPO pumice granules 6 L

9.4/10about £29.78

View offer

Peat-free, dust and what the bag must say

Peat-free is wording on that bag. The planned 2024 amateur peat-sale ban was not enacted. A March 2026 Defra written answer still says the government will legislate when parliamentary time allows. The Royal Horticultural Society’s rule is that if the bag does not say peat-free, it most likely is not. Organic does not fill the gap. UK GROW cactus titles and a Topline citrus bullet print peat-free. The houseplant bullets do not. The Westland orchid listing does not either, even where the manufacturer site does. Westland’s dust line is a ventilated place, no inhaling, gloves, washed hands, and a dry, frost-free store. Houseplant bullets say nutrients for about six weeks, then a liquid. COMPO’s 96 per cent less CO2 line, and any line that granules prevent fungus gnats, stay manufacturer claims. Pot, ratio and first water are on how to use Seramis granules.

What this page leaves to the next click

This page does not rank the ten listings or set a watering amount. A 7.5 litre sack from another shop is not a row here. Match the next click to the question you still have.

Common questions

Do I buy loose granules or a mix that names Seramis?

Buy loose mineral if you want a reusable store, a top dressing or a drainage layer. Buy a named mix if you want compost for one plant group: orchid, houseplant, cactus or citrus. The mix feeds for a few weeks, then needs a liquid. It is not something you rinse and reuse.

Which bag size do I need for one 14 cm pot?

Westland orchid and the UK GROW cactus 4 L listings both say a 4 litre bag fills a 14 cm pot. That claim is for those composts, not for a 10 litre Hydroleca sack. One peace lily in a cachepot is a loose-granule job if you want a closed mineral fill, not a 50 litre cactus mix.

Does organic on the bag mean peat-free?

No. The Royal Horticultural Society treats organic and environmentally friendly as different words. Only peat-free on that bag counts. There is no enacted UK amateur peat-sale ban as of March 2026. If the listing does not print peat-free, do not fill the gap from another page.

Why is a 1 L LECA grit dearer per litre than 10 L Hydroleca?

Because you are paying for a trial pack. Invigortex 1 L is about £7.50 a litre at about £7.49. Hydroleca 10 L is about £1.36 a litre at about £13.55. The small bag makes sense only if you want to test grit in one or two pots before you buy volume.

Can I use orchid mix on ordinary houseplants?

Westland sells that 4 litre bag as an orchid mix with pine bark and Seramis. The manufacturer page says it is not a general houseplant compost and not for ericaceous plants. Use it for an orchid repot. For mixed indoor pots, look at a houseplant mix or at loose granules.

What should I check if the sack is unmarked?

Check the order against the listing: litres, the product type, and whether a label names the brand. Unmarked sacks and split packs show up in the UK GROW houseplant reviews. Volume and description must match under the Consumer Rights Act 2015. That is a goods issue, not a watering issue.

Seramis granules for houseplants