You don't need mag and calcium IMO
. Just get the alk
kit. You don't have enough coral to use up calcium or mag. Salifert test kits are 10 times better than API. I'm not a fan of red sea kits, but some like them.
, don't switch from Oceanic. It's a fine salt. The only thing is the alk
. Other salts have their issues. None of them are totally awesome ....at least not lately. Years ago I used to run large coral tanks on just water changes, but it seems like that's a thing of the past.
No way around good quality test kits any more