pump size
 

I have a 30G round bucket for salt mixing. Will Mag Drive 3.5 is good enough?

As long as it make the water turn. I used a blower for a while till I got a pump

it will mix yes it will just take a while and draw alot of power

i use a korolia 4 1200 gph to mix water in a 55G drum the support piece to the magnet broke so its virtually useless in the tank but it only draws 10 watts or so if i remember correctly and will mix 55 gal clear in no time

A MaxiJet 1200 will mix 30 gallons of water no problem and is much cheaper and easier to clean.