We don't really put much stock in strip testing--they simply aren't reliable. They are okay to tell you that there "is" or "is not" chlorine in the pool, but not reliable enough to tell you "how much", which is what you're going to need to know. We very highly recommend getting your own drop-based test kit--the one we like is the K-2006, which is available online several places, but at a good price at the Amazon link in my sig below. At the very least, check with your local WalMart and see if they have the hth 6-way drop-based kit,which is a re-labeled Taylor kit, and is compatible with the K-2006. And if that doesn't work, you can take a sample of your water to the pool store (IF they use drop testing, not strips!) and ask them to test it for you and give you a printout of results. We need numbers, not "good" or "too low". Just don't let them sell you the list of stuff they'll try to convince you that you need--just smile and tell them that you have it at home. Pool store testing is designed to sell chemicals, so sometimes are not reliable either, but better than strips, at least in most cases.

Sustain appears to be a cal-hypo system, and you can buy cal-hypo much cheaper than what I've seen Sustain products advertised as. However, You'll really need to know a calcium hardness number to know whether it's okay to continue using cal-hypo without running the risk of cloudy water, which happens when calcium levels get too high.

Janet