If im not mistaken thats about 10 microsiemens which is like RO water. I take my readings with a Hanna combo pH & EC, i used to use the test kit with the drops and found it bothersome, innacurate, and time consuming. I'm going to wait for your final report on water param after geting it tested today. I buy the 5lb crushed oyster shell from Jehmco, which is super cheap about $5. I put about 30 lbs in my sump to get the reading close to 100ppm. I also supplement their food mix with coral calcium, but the best way to get their calcium for bone development is from their gills through their water. I dont know what the optimal reading should be, so those tds experts want to chime in, id like to see the responses.
Angel