Complete beginner to saltwater here. We have a 75 litre tank and have bought salt and am ready to mix it up. But apparently you can't mix the salt in the tank and it needs to sit for a day or two in another container - I don't have another 75 litre container though! I've got a 25 litre one, so could I either:

(a) mix up a third of the salt & water in the 25 litre container and then do that 3 times, to equal the 75 litres

or, preferably:

(b) could I mix all the salt in one lot of 25 litres (which will mean the salt ratio is 3 times too strong) and put that in the tank then add 50 litres of unsalted water to bring it back to the correct ratio?

I have no experience in marine/saltwater-keeping, and am not sure anyone is currently using the forum who does. *However*, Option (a) seems the most foolproof method, ensuring an appropriate mixing of the salt in the water, where Option (b) seems riskier. [Sorry - I know that's not the answer you wanted, but I get the impression there's little scope for risk-taking in marine fishkeeping.]

Thanks very much!