Non Technical (cheap) Method.....but it works.
Use Cooking Salt (not Table Salt) from your local supermarket, 3-4 desertspoons of salt per litre of tapwater will do.
If the pH is a tad low 7.2 or under add a little Bicarbonate of Soda to increase to around 8.0
Brineshrimp are the two orange jars, second shelf...
Regards
C
Cattle salt from a feed store is as cheap as I've been able to find it, $4 for a 70 pound sack. Unless you hatch a lot of bbs all the time get the pickling salt from the grocery store.