Hydroponic fertiliser for houseplants in LECA or a jar

Updated: October 2026

You have a monstera in LECA by a UK window, or a cutting in a jar, and the feed you were offered is a coco chart, a bloom set, or a bottle of fish emulsion. That is an easy wrong buy for a flat.

You have a monstera in LECA by a UK window, or a cutting in a jar, and the feed you were offered is a coco chart, a bloom set, or a bottle of fish emulsion. That is an easy wrong buy for a flat. This page stays on volume and smell for hydroponic fertiliser for houseplants, using the bottles in the hydroponic fertiliser comparison. It is not a tomato chart. The fork is on the hydroponic fertiliser buying guide. It is not a laboratory trial. A qualifying purchase can earn a commission at no extra cost to you.

Our top picks

Badge	Product	Volume on the title	Listing dose	Nutrient role	Note	Price	Offer
Best overall	BioBizz BioBizz Fish-Mix, 1 litre	1 litre	1:0, not a usable rate	Organic fish emulsion	9.4	about £12.56	View offer
Best value	Growth Technology Growth Technology Formulex, 1 litre	1 litre	1:99	One-part mineral solution	9.2	about £11.77	View offer
Alternative	Growth Technology Growth Technology Formulex, 5 litres	5 litres	Not a usable figure	One-part mineral solution	9.2	about £29.89	View offer

Best overall

BioBizz BioBizz Fish-Mix, 1 litre

9.4/10about £12.56

View offer

Best value

Growth Technology Growth Technology Formulex, 1 litre

9.2/10about £11.77

View offer

Alternative

Growth Technology Growth Technology Formulex, 5 litres

9.2/10about £29.89

View offer

On this page

1.A jar is not a coco pot
2.Formulex on LECA and in a kit
3.Smell, if the bottle is fish emulsion
4.Small bottles that do not solve a windowsill

A jar is not a coco pot

A jar or a LECA reservoir has no soil to buffer a mistake, and the volume is often under a litre, not the 10 litres a CANNA chart is written for. The Royal Horticultural Society notes that the solution gets stronger as plants drink, and that a fresh mix about every two weeks is the usual rhythm. A full A and B coco or bloom chart is the wrong default for that jug. On this shelf the one-part bottle is Formulex, not CANNA Coco and not Aqua Flores. Coco A and B at about £17.56 is built for coir, and Aqua Flores at about £23.01 is a recirculating bloom set with nine reviews. Hydroponic Houseplant Focus is written for LECA and is not one of the eight listings here, so it is not scored.

Formulex on LECA and in a kit

Formulex 1 litre is about £11.77, with 4.6 from 140 reviews and 21 United Kingdom texts stored. Those notes include LECA, monstera, and chilli seedlings. The Amazon ratio field is 1:99. The number-of-items field says 1000 against one bottle. Unit count and liquid volume say 1 litre. The maker guide, which is not the same string as 1:99, says 10 ml per litre in hydroponics and 5 ml per litre for soil or a foliar spray. For a half-litre LECA reservoir that is 5 ml if you follow the hydroponic rate. Do not copy the Houseplant Focus rate onto this bottle. The bullets say the pH is buffered and do not print a target number. The 5 litre at about £29.89 has a dose field that is not a usable figure. For one or two plants, the 1 litre matches the job.

Testsieger

BioBizz BioBizz Fish-Mix, 1 litre

9.4/10about £12.56

View offer

Smell, if the bottle is fish emulsion

Fish-Mix is about £12.56, 4.7 from 2,059 reviews, and the highlight does include hydroponics. The bullets stress outdoor soil. The first 50 UK texts treat smell as the main complaint. Used immediately, some reviewers call it mild. A mix left for a day or more, including overnight indoors, is described as very strong. Canterbury Hydroponics says it is not really suitable indoors because of the smell. A dog followed the smell in one text, and a cat licked the bottle in another. That is not a safety test, and no kept listing here states pet safety. The item weight is 227 g against a 1 litre title, and the ratio field is 1:0. Mix only what the plant will take at once. If you wanted a quiet one-part feed for LECA, Fish-Mix is the skip.

Small bottles that do not solve a windowsill

A 50 ml or 110 ml title looks like a flat-sized buy, and these three do not solve it. The generic bottle is about £5.56, with no stored text, a 50 ml title, and a unit count of 1.0 millilitre. Qzdtue is about £9.09, one review at 1.0, a 110 ml title, the same 1 ml unit count, and a label the reviewer says is only in Chinese. Nouri is about £6.99 of A and B with no star line and a granule field against a 50 ml title. You still need an English rate and a volume the fields agree on. For LECA or a jar, buy Formulex 1 litre and refresh on the two-week rhythm. The best hydroponic fertiliser UK page separates coir and a recirculating tank from this windowsill. The pour order is on how to mix hydroponic nutrients.

Common questions

What should you put in a LECA reservoir if you want one bottle?

Formulex 1 litre at about £11.77. Stored UK notes include LECA and monstera. The maker guide says 10 ml per litre for hydroponics, so a half-litre reservoir is 5 ml. The Amazon field says 1:99. Hydroponic Houseplant Focus is not in this comparison.

Is Hydroponic Houseplant Focus on this comparison?

No. It is a Growth Technology feed for LECA, Lechuza-Pon, and water culture, and it is not one of the eight listings. Do not copy its millilitres onto Formulex.

How much Formulex do the maker instructions say for hydroponics versus a foliar spray?

The grower guide says 10 ml per litre in hydroponics and 5 ml per litre for soil or a foliar spray. Amazon prints 1:99 on the 1 litre, and the 5 litre dose field is not a usable figure. The listing does not give a pH number to hit.

Will Fish-Mix smell in a flat if you mix a jug and leave it?

Yes if you leave it. Used immediately, some people call the smell mild. Left overnight indoors, it is described as very strong. Mix only what you will use straight away. The 2,059 reviews do not cancel that pattern.

Are the 50 ml and 110 ml bottles a sensible windowsill size?

The title looks convenient, and the fields do not back it up. The generic bottle pairs 50 ml with a unit count of 1.0 millilitre and has no review text. Qzdtue pairs 110 ml with 1.0 millilitre, and the only review says the label is in Chinese. Nouri has no star line and a granule field.

Is CANNA Coco or Aqua Flores a houseplant default?

No. CANNA Coco is a two-part feed for coir, charted around 10 litres. Aqua Flores is a recirculating bloom nutrient, with nine reviews and no Amazon dose. For the windowsill, stay with the one-part litre.