I'm a beginner in the saltwater scene, well I havent even started yet! But anyways I have my tank all set up right now, got the filters running and one powerhead just to move and aerate water, it's a 20 gallon tall, with a aqauclear powerfilter, and an aquaclear powerhead i think like 250 gph maybe. Everything is running, but I would like to know how much salt I need, I see the bags in stores that say like 20 gallon mix and 50 gallon mix etc, do I add the whole 20 gallon mix bag to my tank, or do I add a little at a time and check the salinity? And my next question is, is the salt in the tank going to last, or am i going to be constantly adding salt? Thanks guys for any help