gettaReef
Valuable Member
If the 713 is +/-.04 then a reading of zero means you are most likely pretty darn close to the preferred phos level. I agree that a 736 is better for those who want the most accurate reading like for a SPS system, but IMO pple can get by just fine and get a relative digital reading with a 713. I have both bc I first bought a 713, and upgraded to a 736 when I discovered it was more accurate. When I test and the 736 gives me a desired reading of phos between .01 - .04 after conversion, the 713 always reads zero - .01. With this, one could get by as long as the 713 reads a zero-.01
