Urgent help required: Artifical Seawater salt

I need some help as no-one I have spoken too can offer the right knowledge
without putting down the information, someone else has told me.

What is a good product to make artificial seawater, that is easy to use and
can be used buy a moron like me. I want to use it for seahorses, I live in
Perth Western Australia and am desperate to find something, that isn't going
to cost me an arm and leg, I'm am married with three children and we survive
on a disability pension, we do not have very much disposable income.

I want to set this up for my family as a special present, because they do
without so much.

Is there no general consensus on the best product?????

Please help.

Regards
Mark