VA, do you have a proper test kit? One that contains the FAS-DPD powder chlorine tester? The Taylor K-2006C or the TF-100 are both about the same in quantity of testing reagents, but the TF-100 is cheaper and the reagents are sized more for the tests you do the most.
You can obtain both from
TFTestkits.net or Amazon. I would suggest going thru tftest.net because they ship out of NC so its fastest. They also sell the test kit to monitor your salt levels. That's important with a SWG.
Once you obtain the kit you'll have the tools you need to test for : FC, CC, pH, TA, CH and CYA, and optionally the salt level.
You'll need to run a full set of tests (about 10 min time) and then take those numbers up to the PoolMath app at the top of the page and input the numbers in to the "Now" column.
You need to have an idea of what your goal target number is and input that in to the "Target" column. It will then scrunch the numbers and advise you.
Please remember to fill out your pool gallon size at the top, and your surface (plaster) at the bottom. You want to take "troublefreepool.com" and "SWG" option choices too.
Here is a rough guide to strive for-->
Pool School - Recommended Levels
Please let us know if you can do this?
As for worry about nitrates and phos.... feh! Not even on my mind. Proper chlorine levels make them unable to cause problems.
For reference, on my SWG pool I can test once or twice a week and be done! It rarely needs any other chemical. I'd say that it is as TROUBLEFREE as they come!!
Maddie