My tanks only 30 gallons and I never need to dose anything cus it's small but my brother has two tanks 1 is 150 and the other is 90 and they share the same
Sump so he has to dose but very little and also he had quadruple the corals I have.. rea sea may cost a few more bucks but u don't have to buy calcium and what not to add to the tank unless ur setup is big like my brothers..just my two cents