Lawn & garden
Chempak Formula 8 Low Nitrogen Feed dupe
Why pay around £8.99 for Chempak? The bulk active is Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20) — 48% less per working litre than a typical shelf pack.
From the retail pack to the active and the mix
1 · Retail
Chempak Formula 8 Low Nitrogen Feed
750 grams · £8.99 typical snapshot
Soluble salt carrier and chelated traces
2 · Active
Soluble NPK 12.5-25-25 with traces
62.5% on the label
66455-26-3N + P2O5 + K2O
Bulk Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20)
3 · Mix
2 g/L
£0.02 per working litre · 48% less than the shelf pack
- Active
- Soluble NPK 12.5-25-25 with traces
- CAS
- 66455-26-3
- Dupe
- Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20)
- Saving
- 48% / L
Saving is per litre of working-strength mix versus a typical pack price, not versus the DIY kit total. Shop prices move — always check the listing.
Label teardown
What the pack promises versus what the label chemistry actually is.
The marketing claim
“Low nitrogen — matures growth on heathers, conifers and vegetables”
The chemical reality
This is not Miracle-Gro 20-20-20 and it is not Tomorite 4-3-8. Formula 8 is a low-N, high-P/K soluble at 12.5-25-25 for ripening onions, leeks, heathers and conifers. The same analysis sells as hydroponic bloom / PK-heavy soluble powder by the kilogram — some shops now label the range Incredigrow.
Active vs filler
62.5% Soluble NPK 12.5-25-25 with traces · 38% carrier / filler — Soluble salt carrier and chelated traces
- Typical retail
- £8.99
- 750 grams
- Estimated active cost
- £7.13
- Scaled from bulk £9.50 / 1 kg
- Indicative markup
- 1.3×
- Snapshot maths, not a live shop price
The Marketing Claim & The Catch
A 750 grams pack of Chempak Formula 8 Low Nitrogen Feed typically retails around £8.99 in lawn & garden. That is a UK shelf-price snapshot for the maths on this page — not a live shop quote or a manufacturer RRP. Listings, sizes and deals move. The marketing line is that you are buying a finished lifestyle product, not a weighed chemical.
On the pack: Low nitrogen — matures growth on heathers, conifers and vegetables; Extra phosphate and potash for a firm, ripe finish; and Seven essential trace elements.
The catch: This is not Miracle-Gro 20-20-20 and it is not Tomorite 4-3-8. Formula 8 is a low-N, high-P/K soluble at 12.5-25-25 for ripening onions, leeks, heathers and conifers. The same analysis sells as hydroponic bloom / PK-heavy soluble powder by the kilogram — some shops now label the range Incredigrow.
- “Low nitrogen — matures growth on heathers, conifers and vegetables”
- “Extra phosphate and potash for a firm, ripe finish”
- “Seven essential trace elements”
Proprietary Blend & Dosage Breakdown
The labelled active is Soluble NPK 12.5-25-25 with traces at 62.5%. Everything else in the pack is soluble salt carrier and chelated traces.
Even when the pack is sold as “pure” or ready-to-use, the dose that actually does the work is Soluble NPK 12.5-25-25 with traces. The rest is how they get it into a bottle you will pick up.
Branded working strength is whatever comes out of the bottle. The bulk alternative is 62.5% Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20), mixed to 2 g/L.
- Labelled active
- Soluble NPK 12.5-25-25 with traces
- 62.5%
- Carrier
- Soluble salt carrier and chelated traces
- Retail pack
- 750 grams · £8.99
The Active Chemical Alternative (Dupe Stack)
The dupe stack is Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20) at 62.5% bulk. Indexed as CAS 66455-26-3, formula N + P2O5 + K2O. Buy it as 1 kg for around £9.50 from Amazon UK.
Working strength: 2 g/L. Indicative cost £0.02 per diluted litre — 48% below a typical branded pack on a per-litre basis, before you reuse leftover bulk.
Follow the mixing method and the supplier SDS. Wear the listed PPE. Do not mix incompatible oxidisers, acids or ammonia.
- Wear gloves if you have broken skin. Avoid inhaling the fine powder.
- Dissolve 2 g of 12.5-25-25 (or a near bloom analysis such as 10-30-20) per litre of water — the same order as 2 Chempak measures in 5 litres.
- Feed every 7–10 days on moist compost. For every watering, use 0.5 g/L.
- 1 kg at 2 g/L is about 500 litres of working feed. A 750 g Chempak box is 375 litres at the same rate.
- This is a feed, not a pesticide. Store dry.
Dilution recipe
5 L sprayer
Working strength 2 g/L. Educational estimate from the listed ratio — check the SDS before you mix.
Chemical
10 grams
Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20)
Water
5 litres
Carrier / diluent
0% concentrate · 100% water by working volume (solids are dissolved into the water share).
Required PPE
Loading calculator…
Side-by-Side Price & Potency Comparison
Head-to-head comparison
| Measure | Retail brandedChempak | Raw active dupeDupeStack |
|---|---|---|
| Product | Formula 8 Low Nitrogen FeedAmazon UK search — listing, not a confirmed seller | Soluble fertiliser 12.5-25-25 (or near PK bloom 10-30-20) |
| Pack / unit | 750 grams · £8.99 | 1 kg · £9.50 |
| Active | Soluble NPK 12.5-25-25 with traces at 62.5%Carrier: Soluble salt carrier and chelated traces | 62.5% bulkN + P2O5 + K2O |
| CAS number | Not disclosed on pack | 66455-26-3 |
| Working strength | Ready-to-use pack | Dilute 2 g/L |
| Cost per litre | £8.99 / pack | £0.02 / L mixed from bulk |
| Headline saving | Baseline | 48% cheaper |
| COSHH / PPE | Follow the branded SDS | Gloves. Chemical-resistant gloves (nitrile or neoprene)Ventilation. Use outdoors or with mechanical extraction |
Active ingredient and cheaper alternative — FAQ
Is Chempak Formula 8 the same as Formula 3?
No. Formula 3 (Incredigrow All Round) is balanced 20-20-20 — the same analysis family as Miracle-Gro liquid powder. Formula 8 is 12.5-25-25: deliberately lower nitrogen and higher phosphate and potash for mature growth. Do not swap them on leafy salads if you want soft top growth.
What rate matches the spoon on the pack?
Normal strength is 2 level measures in 5 litres — about 2 g per litre. Weak every-watering feed is 1 measure in 10 litres (~0.5 g/L). Weigh the first spoonful once; after that the maths stick.
How do you mix the Formula 8 Low Nitrogen Feed dupe stack?
Wear gloves if you have broken skin. Avoid inhaling the fine powder. Dissolve 2 g of 12.5-25-25 (or a near bloom analysis such as 10-30-20) per litre of water — the same order as 2 Chempak measures in 5 litres. Feed every 7–10 days on moist compost. For every watering, use 0.5 g/L. 1 kg at 2 g/L is about 500 litres of working feed. A 750 g Chempak box is 375 litres at the same rate. This is a feed, not a pesticide. Store dry.
DupeStack provides chemical concentration data and educational mixing guides only. Wellness pages compare food supplements, not medicines or prescribed treatments. Always review the supplier Safety Data Sheet (SDS) and comply with UK Health and Safety Executive (HSE) and COSHH regulations when handling concentrated substances. Mixing and storage are at your own risk. Some links are affiliate advertisements (Amazon Associates, eBay Partner Network, and Awin when those programmes are live). Commissions do not change listed concentrations or calculator output.
Related guides
Lawn guide
Lawn and plant food labels decoded: NPK without the brand box
What 7-7-7, 5.3-7.5-10 and 12.5-25-25 actually mean, and which DupeStack teardowns match Growmore, Q4, Chempak and tomato feeds.
Lawn guide
Weedkillers decoded: glyphosate vs triclopyr — paths, brambles and lawn
Pathclear RTU, Resolva Xpress pelargonic, Doff mecoprop-P, Weedol Lawn MCPA three-way, SBK brushwood killer and ferric slug bait use different actives. Match the molecule to the weed — and never swap without reading the label.
Lawn guide
Garden tonics decoded: seaweed, chelated iron, Epsom and rooting powder
Kelp extract, Fe-EDDHA, Epsom salts, IBA rooting powder and foliar soap are not NPK bags. Match the deficiency or the cutting — then buy the bulk salt, not the sachet.
More teardowns
Lawn & garden
Miracle-Gro Organic Liquid Seaweed
Miracle-Gro
- Retail pack
- £13.501 litre
- Raw active
- Soluble Ascophyllum nodosum kelp powder84775-78-0
A watered-down cold-pressed kelp extract. Soluble Ascophyllum nodosum powder is the same crop, sold by the kilogram to hydroponic growers, at a fraction of the bottled price.
Lawn & garden
Evergreen Complete 4-in-1 Lawn Feed & Moss Killer
Evergreen
- Retail pack
- £24.00100 m² box
- Raw active
- Agricultural soluble iron(II) sulphate heptahydrate7782-63-0
The moss-blackening punch is ferrous sulphate — the same agricultural iron used on bowling greens. The 4-in-1 box is mostly filler, NPK dust and a brand. Buy the salt.
Lawn & garden
Growmore Garden Fertiliser
Growmore
- Retail pack
- £9.504 kg
- Raw active
- Agricultural NPK 7-7-7 compound fertiliser66455-26-3
7-7-7 is a commodity NPK blend. The cardboard box is a portioned sack of agricultural compound fertiliser. Buy it by the 25 kg bag from a merchant, not 4 kg at a time from a garden centre.
£18.50Save 48% / L
Indicative DIY stack