Every bucket of salt I've seen, will list how many gallons of SW
it can create. Keep in mind to look at what SG
their mix ratio equals.
Most I've seen are mixing at 1.018 - 1.020 SG
...typically fine for FOWLR
, but reef tanks run a little higher salinity, so you'll get a few less gallons out of a bucket.
Around here, the 5gallon bucket of Oceanic (260gals I think?) is around $50 on sale. SW
isn't real big here, so everything's at a bit of a premium price.