The best effective microorganisms, compared.
Top pick: Microferm 5 litre ready liquid Best value: Microferm 5 litre ready liquid – About £8.98 per litre of ready liquid at about £44.90, the lowest ready-liquid rate in the set. One review does not make this a quality verdict. Updated 22.10.2026.
Effective microorganisms, as UK sellers use the name, are a mixed culture of lactic acid bacteria, yeasts and phototrophic bacteria. You buy them for soil, a compost heap or a bokashi caddy, either as a dormant mother solution or as a liquid that is already active. A separate powder in the same search is a different product, for coco or hydroponic feeds, and it is not a substitute. The checks that stay useful when the bottles change are stage, pack size and whether the listing is the mixed culture or a powder. Those checks are set out in the [effective microorganisms buying guide](/hub/diy-supplies/effective-microorganisms/sub/effective-microorganisms-buying-guide). A mother solution is not ready for soil until it has been activated. A ready liquid is sold to dilute. Neither is a pesticide, a pet treatment or a fish medicine, and this category does not print a pesticides authorisation number. A large canister is the wrong first buy for a kitchen caddy.
Effective microorganisms, as UK sellers use the name, are a mixed culture of lactic acid bacteria, yeasts and phototrophic bacteria.
22 products checked · 58 hrs invested · +18,400 readers
Swipe for more
1-2 of 6
Personal buying guide
Question 1 of 2
Which stage do you want?
The 5 litre Microferm is the best value on pounds per litre of ready liquid: about £44.90 is about £8.98 per litre, against about £14 for the 2 litre pack. The adjusted score is 75 because there is one five-star rating, from Germany, which says the buyer uses it on a pond. That is not a fish-safety test and not a UK review. The title says ready to use. Compost and silt are named in the bullets without a rate.
Pros
Cons
Best for: You want already active liquid and the lower price per litre, and you will use 5 litres.
Less suitable: You want a UK review sample, a mother culture, or a stated fish treatment.
Specifications
Common questions
Is this the best-value pack on price per litre?
Among ready liquids in this set, yes. About £44.90 for 5 litres is about £8.98 per litre. The 2 litre pack is about £14 per litre. The badge is that price. The file has one review.
Does the review say it is safe for fish?
No. One German review says the buyer uses it for a pond and calls it a good product. The file has no fish-safety line.
The 2 litre Microferm is the ready-to-use liquid at about £27.99, about £14 per litre, with an adjusted score of 75 from a single five-star rating. The only review is a UK line that says it works great. The bullets mention gardens, compost, odour, flies and silt in ponds, and they do not give a rate. The pet question is unanswered. It costs less to try than the 5 litre pack and more per litre.
Pros
Cons
Best for: You want already active liquid and a smaller outlay than 5 litres.
Less suitable: You want the lower price per litre of ready liquid, or a mother culture to activate.
Specifications
Common questions
Do you activate this 2 litre pack?
The title says ready to use and the bullets call it already active. This file does not print an activation step. The pet question is asked and not answered.
What does the UK review say?
One verified review from the United Kingdom, dated 6 February 2026, says it works great. There is no second review in the file.
The 1 litre Moutta EM-1 is the top pick in this set because it shares the highest adjusted score, 78, with the other EM-1 sizes and costs about £39 per litre of concentrate rather than about £88 for the 250 ml. The 10 litre pack is cheaper per litre and costs about £299.99, so it is not the home starting size. You still have to activate it. The 4.5 from 27 is the same line printed on the smaller and larger canisters, and the four short reviews in the file are not from the United Kingdom. There is no pet answer and no MAPP number.
Pros
Cons
Best for: You want a mother culture you will activate, in a size cheaper per litre than 250 ml and smaller than 10 litres.
Less suitable: You want liquid you can dilute today, or a labelled pet or pond treatment.
Specifications
Common questions
Does this canister need activating?
Yes. The listing says activation is required before the use it describes. A notice is included. The pet question is asked and not answered, and there is no MAPP number.
Does the file say it is safe for pets?
The listing asks the question. The spec block does not print an answer. Do not read a soil claim as a pet treatment.
The 250 ml EM-1 is the same mother culture as the 1 litre, at about £21.99, which is about £88 per litre of concentrate. The adjusted score is 78 because the file prints 4.5 from 27, the same line as the other EM-1 sizes. It is the lowest cash outlay if you only want to try an activation, and it is the dearest EM-1 per litre. Activation is still required. The pet question is unanswered.
Pros
Cons
Best for: You want the smallest EM-1 canister and you accept the higher price per litre.
Less suitable: You want the lower price per litre of concentrate, which is the 1 litre, or a liquid that is already active.
Specifications
Common questions
Is 250 ml ready to put on the soil?
No. The bullets say activation is required. This file does not print a mixing ratio. It is the lowest cash price among the mother-culture canisters, at about £88 per litre of concentrate.
Why is the star line the same as the 1 litre?
This file prints 4.5 from 27 and the same four short reviews as the other EM-1 sizes. None of those reviews is marked United Kingdom.
The 10 litre EM-1 is about £299.99, about £30 per litre of concentrate, which is the lowest concentrate rate in the set. The adjusted score is still 78, tied with the smaller canisters, because the star line is the same 4.5 from 27. It stays off the top-pick slot because that outlay is not a first home canister. Activation is required. The vegetable-garden question is unanswered, and no review in the file talks about this size.
Pros
Cons
Best for: You already activate EM-1 often enough to finish 10 litres of mother culture.
Less suitable: You are buying a first canister, or you want liquid that is already active.
Specifications
Common questions
Is the 10 litre canister already active?
No. The title calls it a stock solution and the bullets say activation is required. The vegetable-garden question is asked and not answered.
Do the 27 reviews describe this size?
The file prints the same 4.5 from 27 and the same four short reviews as the smaller EM-1 files. None of them mentions a 10 litre pack.
BioBizz Microbes is a 150 g powder at about £49, kept because it is a plant microbial product and not because it is EM-1. The adjusted score is 72 from 4.2 and 14 ratings. The file does not include 14 review texts. The one visible review body is empty. The listing ratio and the brand sheet do not use the same unit, so neither line is treated here as a dose. There is no activation step and no answer to the organic question. The rank line sits under hydroponic nutrients.
Pros
Cons
Best for: You already use BioBizz and want this powder, reading the brand sheet rather than the amazon ratio line alone.
Less suitable: You want EM-1 or Microferm.
Specifications
Common questions
Is this the same as the mother culture?
No. The title is a powder. The file does not call it a mother culture or a ready liquid. The rank line sits under hydroponic nutrients.
Does the file say it is organic?
The listing asks. The spec block does not answer. The only visible review body is empty. The listing ratio and the brand sheet do not use the same unit.
Shelf prices, star lines and review counts are the amazon.co.uk figures stored for these six listings. This is not a laboratory test. The score starts from the star rating times 20, then deducts 12 points when the count is 10 to 29 and 25 points when the count is under 10. The three mother-culture sizes share 4.5 from 27, so that tie is broken by pounds per litre among packs a home order can finish. Best value is a different listing: the lowest pounds per litre of ready liquid. Seller pages were used only to tell a mother culture from a ready liquid.
Amazon star line
40%The base is the amazon.co.uk star rating times 20. A missing rating line would stay at 0 and could not take a badge. None of these six files is missing a star line.
Review-count adjustment
25%No deduction at 30 reviews or more. Deduct 12 points when the count is 10 to 29, and 25 points when it is under 10. A single five-star rating cannot lead.
Stage and home pack
20%Mother culture still needs activation. Ready liquid does not. A tied mother-culture score is broken by a pack a home order can finish, which leaves the £299.99 canister off the top-pick slot.
Price per litre
15%Best value is the lowest pounds per litre of ready liquid. The powder is not in that per-litre race. The value badge is not the same listing as the top pick.
Buy the stage before the litre headline. A mother solution has to be activated. A ready liquid is already active. A powder in the same search is a different product. Then check pack size, pounds per litre of what is in the bottle, and whether the star line is a shared catalogue figure. None of these listings is a pesticide, a pet treatment or a fish medicine.
Effective microorganisms, as UK sellers use the name, are a mixed culture of lactic acid bacteria, yeasts and phototrophic bacteria. Home gardeners buy them for soil, compost or a bokashi caddy. The same search also returns a powder for coco or hydroponic feeds. That powder is not the mixed culture. Split the bottles by stage before you split them by price. A mother solution has to be activated before it is a garden liquid.
A mother solution is not ready for soil until it has been activated. A ready liquid is already active. Treating every bottle as ready, because the search said effective microorganisms, is the miss. Brand notes also say chlorinated water is a reason an activation fails. This page does not set out the steps.
The 10 litre mother culture is the lowest price per litre of concentrate and costs about £299.99. That is the wrong first canister for a kitchen caddy or a trial. The home starting size in this set is 1 litre.
A soil-life claim is not a pesticide claim. No file prints a MAPP number. Pet questions are asked and not answered. A pond review is not a fish-safety test. Bokashi solids are pre-compost, not finished compost on the day you empty the bin.
The first check is the job and the stage, because these rows are not substitutes. Soil, compost and a bokashi caddy are the liquid-culture jobs. A kitchen caddy does not need 10 litres of concentrate. A mother solution has to be activated. A ready liquid is sold already active, and the titles in this set say which is which. The powder is for germination and early growth in coco or hydroponic feeds. It is not EM-1 and not Microferm.
On the stored amazon.co.uk prices, mother culture runs from about £21.99 for 250 ml to about £39 for 1 litre and about £299.99 for 10 litres. That is about £88, £39 and £30 per litre of concentrate. Ready liquid is about £27.99 for 2 litres and about £44.90 for 5 litres, about £14 and £8.98 per litre. The powder is about £49 for 150 g and is not in the per-litre race. The three mother-culture sizes share 4.5 from 27 and the same short reviews, none of them UK text for that canister.
Three typical situations, each with a recommendation from this comparison.
You want a mother culture for soil or compost and you will activate it before use. The 1 litre EM-1 is the top pick at about £39, score 78. It is cheaper per litre of concentrate than the 250 ml and smaller than the 10 litre canister. The 4.5 from 27 is shared across those sizes and is not a UK write-up of this canister.
You want liquid that is already active and you will use 5 litres. The 5 litre Microferm is best value at about £44.90, about £8.98 per litre, against about £14 for the 2 litre pack. The score is 75 from one German review that mentions a pond. That is not a fish-safety test.
You already feed plants in coco or a hydroponic tank and you want this powder. BioBizz Microbes is 150 g at about £49, score 72, from 4.2 and 14 ratings. It is not a mother culture and not a ready liquid. The listing ratio and the brand sheet do not use the same unit.
The top pick is the 1 litre EM-1 mother culture at about £39. It scores 78, level with the other EM-1 sizes, and it is the home starting size: about £39 per litre of concentrate against about £88 for the 250 ml. The 10 litre canister is cheaper per litre and costs about £299.99, so it does not take that slot. Best value is the 5 litre Microferm at about £44.90, about £8.98 per litre of ready liquid. That score is 75 from one review, which is not from the United Kingdom and not a fish-safety test. The BioBizz powder is a different product and has no badge.
Microferm 5 litre ready liquid
About £8.98 per litre of ready liquid at about £44.90, the lowest ready-liquid rate in the set. One review does not make this a quality verdict.
Editorial
Peter F. is the editor for DIY & tools at productscompared.co.uk. Comparisons in this category are checked against amazon.co.uk listings, review evidence and public UK sources.
Guides on what to look for, how to use a product, and common mistakes.
Public UK sources and the amazon.co.uk listings compared on this page. Updated 22.10.2026.
This page contains affiliate links. If you buy through them, we may earn a commission at no extra cost to you. Prices, stars and review counts are the amazon.co.uk figures already stored for this set. This is not a laboratory test.
