These chemicals can be had at any decent hydroponics store, mail ordered or obtained from drug and hardware stores under the names given in quotes above. Adding that small amount of Potassium sulphate seems kind of silly to me given the amount of potassium available from the KO3 and KP04. It can safely be ignored.

Note that the solution may go a bit cloudy with age. A drop of hydrochloric (muriatic) acid will prevent that, but I don't bother. Double neck dosing bottles are a very convenient way to diespense this stuff. At least one commercial aquarium fertilizer is available in one and it's almost worth buying just for the bottle. The bottles themselves are also available by mail order. When I mix up two litres I put some in such a bottle and just leave the rest in a 2L soda pop bottle, properly labeled.

3 times a week add 10 ml for a 20 gallon tank. Or 1-2 ml daily. Or 15 ml twice a week. This will add 30 ppm nitrate a week to a tank with corresponding correct proportions for the other macronutrtients.

For a 100 gallon tank simply multiply by 5. For a 10 gallon tank divide by 2 and so on and so forth.

-- Richard Sexton, 2006