What kind of tank do you want to have? What are you trying to keep?
Salifert test kits give you precise readings. If you aim at corals, those are a good thing to have.
You should be testing (again, Salifert) for nitrite, nitrate, and ammonia. These cycle back and forth. If you're not seeing algae and your snails are dead, this is not good.
You're in the right place for advice. We just need some tests to go on: Fill in the following: I know you've provided part of it, but let's be thorough.
Temperature:
Salinity:
Alkalinity:
Ph:
Nitrite:
Nitrate:
Ammonia:
Gallons:
Age of tank:
Sump?
Skimmer? type?
refugium?
downflow? type?
Lighting type?
Live rock?
Live sand?
Sand type (aragonite, crushed coral, etc.)
pump (brand and size)
Type of tank intended to be: [lps, sps, combination, fish only]
On any questions which make no sense to you, just put a question mark. If you know you don't have a particular item, put: don't have.
This will let the experts work on your problem and speed an answer for your situation.