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Copper sulphate buying guide

Updated: 23 October 2026

You have a garden job, a school tray, or a traditional name in the search box, and the amazon.co.uk results look like one blue chemical in different sizes. They are not. This copper sulphate buying guide sorts the eleven listings in our [copper sulfate comparison](/hub/diy-supplies/copper-sulfate) by the job first, then by hydrate, grams, and price. A classroom crystal, a cattle footbath, a crop spray, and a pond treatment sit in different legal boxes, and none of these files prints a MAPP number. Shelf prices are the figures stored with the category, not a live check on 20 October 2026. A qualifying purchase can earn us a commission at no extra cost to you. This page stops at the decision.

You have a garden job, a school tray, or a traditional name in the search box, and the amazon.co.uk results look like one blue chemical in different sizes. They are not.

Our top picks

Minerals-water.ltd 500 g copper sulphate pentahydrate

Best overall

Minerals-water.ltd 500 g copper sulphate pentahydrate
8.8/10about £7.97
View offer
Minerals-water.ltd 250 g copper sulphate pentahydrate

Alternative

Minerals-water.ltd 250 g copper sulphate pentahydrate
8.6/10about £5.97
View offer
MAIGORAY 1 kg copper sulphate pentahydrate

Best value

MAIGORAY 1 kg copper sulphate pentahydrate
8.6/10about £7.97
View offer
On this page
  1. 1.Start with the job, not the blue crystals
  2. 2.Hydrate, form, and what the title is selling
  3. 3.Grade claims, residue, and mass
  4. 4.When these listings are the wrong product

Start with the job, not the blue crystals

Write down the job before you compare star ratings. If it is plant protection, weed control, or killing algae in a pond, UK rules want an authorised product, not a raw salt whose title mentions gardens. Approval of an active substance is not authorisation of a product. Supplying a home-made chemical remedy can be illegal. Check the amateur garden database before any pesticidal use. Northern Ireland can differ from Great Britain. None of these files prints a MAPP number. Storage and spills are on the handling guide.

Hydrate, form, and what the title is selling

The usual blue crystal is copper(II) sulphate pentahydrate, CuSO4·5H2O, CAS 7758-99-8. Anhydrous copper(II) sulphate is CAS 7758-98-7, and it is paler. Do not treat those as interchangeable. Copper oxychloride and copper hydroxide are different substances. Two listings are not loose crystals. The pack titled 5 L is two dry pouches, 50 g copper sulphate and 50 g hydrated lime, unit count 100 g, at £9.97. The pack titled 10 L has a unit count of 200 g at £14.97. Do not divide the price by 5 or 10 and call it a price per litre. The hydrate of those copper pouches is not stated. That comparison is on the copper sulphate and lime page.
Minerals-water.ltd 500 g copper sulphate pentahydrate

Testsieger

Minerals-water.ltd 500 g copper sulphate pentahydrate
8.8/10about £7.97
View offer

Grade claims, residue, and mass

High purity, 99%, and 99.9% are seller words unless a number and a certificate are both in the file. Only the 5 kg listing states a minimum assay of 99.5%, with 4.5 from two ratings and no review text. The 250 g pack is £5.97, 4.3 from 188 ratings, about £23.88 per kilogram. The 500 g pouch is £7.97, 4.4 from 159, about £15.94 per kilogram. The 1 kg bucket is the same £7.97, 4.3 from 113, with CuSO4·5H2O and Warning printed. The 5 kg tub is £69.95, about £13.99 per kilogram, dearer than the 1 kg bucket.

When these listings are the wrong product

Neela thotha is £34.20, about £342 per kilogram, with food-style bullets and no rating. Nila thotha is £22.59, about £226 per kilogram, with pentahydrate not stated. Allergen-style lines are seller text, not a food authorisation. A pond treatment is a biocide. Do not pour pesticides down a drain. If the tub has no CLP label, use the Fisher class for this pentahydrate: harmful if swallowed, serious eye damage, very toxic to aquatic life with long lasting effects, signal word Danger. The 1 kg listing prints Warning, which is weaker wording. If these files cannot authorise the job, leave the crystals.

Common questions

Is the blue crystal in these packs pentahydrate or anhydrous salt?
Where the title states pentahydrate, that is the blue crystal, CuSO4·5H2O, not the paler anhydrous salt. The 250 g, 500 g, 1 kg, 5 kg, Birsppy, and 4 oz listings say pentahydrate. The 14 oz listing and both 100 g traditional-name packs do not. The lime kits do not state the hydrate of the copper pouch. If the line is missing, do not guess it from the colour of a stock photo.
Does high purity, 99%, or 99.9% mean a laboratory certificate?
No. Those figures are claims on the listing. Only the 5 kg file prints a minimum assay of 99.5%, and that file has no certificate and no review text. The 4 oz title says 99.9% while a bullet says more than 99%, and its formula line prints CuSO&C. A Fisher extra-pure 5 kg bottle at £145 is a different product.
Why do some UK reviews mention brown or dark insoluble residue?
Reviews on the 250 g, 500 g, and 1 kg listings describe dirt, a dark precipitate, extra water, or a result that looked like technical grade rather than Analar. One 1 kg review says that made the pack unsuitable for crystal growing or water treatment. These are single buyer accounts, not an assay of every batch. They are a reason to doubt high purity until you have a certificate.
Can I use any of these packs on edible plants, a path, or a pond because the title says so?
No. A title, a bullet, or a review does not authorise a pesticide or a pond biocide. None of these files prints a MAPP number. Check the amateur garden database for a product that is legal to use where you are, and remember that Northern Ireland can differ from Great Britain. Do not pour leftover pesticide down a drain.
Which pack is poor value per gram, and which mass is enough for school crystals?
The 100 g packs are about £342 and £226 per kilogram, and the 4 oz pack is about £172 per kilogram if 4 oz is 113 g. The 1 kg bucket is £7.97 per kilogram. A 250 g pack at £5.97, with 188 ratings, is the small stated pentahydrate if you only need a little for a supervised school tray. This page does not describe a crystal-growing method.
The 1.4 kg title also prints an item weight of 1 kg. Which figure do I trust?
Neither, until the parcel confirms it. The Birsppy listing prints 1,400 g in the title and 1 kg on the item-weight line, at £17.97, with the same part number as the 1 kg bucket. If the contents are 1.4 kg the rate is about £12.84 per kilogram. If they are 1 kg it is £17.97 per kilogram.

Related pages

Best copper sulphate

Copper sulphate footbath

Copper sulfate

Copper sulphate and lime mixture for allotment kits

Copper sulphate safety handling before you open it

Sources

Public UK sources and the amazon.co.uk listings compared on this page. Listings stored 20 October 2026.

  1. HSE: garden and allotment pesticides (retrieved 20.10.2026)
  2. HSE: active substance register (retrieved 20.10.2026)
  3. HSE: amateur garden pesticide database (retrieved 20.10.2026)
  4. NHS: poisoning (retrieved 20.10.2026)
  5. GOV.UK: report water pollution (retrieved 20.10.2026)
  6. GOV.UK: pollution prevention for businesses (retrieved 20.10.2026)
  7. Fisher Scientific UK: copper(II) sulphate pentahydrate safety data sheet, part C/8520 (retrieved 20.10.2026)