The sulphate of potash you already have is OK. It is potassium sulphate (K2SO4). The reference to K2O is only the way it's analysed.
I've previously posted convenient sources for KNO3, but you'll also need the K2SO4, as the nitrate doesn't give you enough potassium. http://www.csd.net/~cgadd/aqua/75g.htm is a good link for the calculations.
You'll probably also need Epsom Salts (MgSO4.7H2O)for the magnesium.
All trace element mixes I'm aware of in the UK contain chelated iron. Not quite sure why you wouldn't want iron.

Paul



"Martin" wrote in message ...
Kelvyn

Avonchem will not sell to individuals as I found out today, well they will
sell to anyone as long as they are VAT registered - which seems stupid to
me! and they have a £100 minimum order.

There is also a company called Scientific and Chemical Supplies Limited -
again no sale to those not VAT registered however, if you have a local
aquarist (like I do) they are VAT registered and they should get it for you
if you give them the details. The costs of KNO3 is £31 approx for 1 Kg which
will last 4 years in a 250L tank. K2SO4 is £26 for 1 Kg.

They are pricey but I later found a company that sold me the chemicals over
the phone using a credit card - just try one or two from a search engine and
Im sure one of them will. The main problem is getting them to deal in small
amounts - S&C Supplies Ltd will do that but only to companies that have a
proper turnover.

They are obviously trying to prevent selling to stupid people that want to
make the odd bomb or two. I mean that literally. I would be cautious about
the USA - I would assume that's the sort of traffic customs are looking for
even though it is legitimate.

Martin

"Kelvyn Shaw" wrote in message
...
I called Avonchem today to check if they would sell to private individuals
but they wouldnt. I am thinking about ordering from the USA.