I have been having some algae problems lately so went and tested for phosphates.
RO/DI water '0'.
Salt mix. '.05'.
Added a minuscule pinch of Coral Frenzy to some tank water and tested it. Reading went off the chart.
If anyone has Coral Frenzy could you please test and post reading? Maybe I am missing something. I dropped a tiny pinch in a quart of fresh salt mix and tested 15 minutes later after the Coral Frenzy settled to the bottom.

Are you testing TDS? It sounds like your testing TDS in the mixed water and IN YOUR TANK. Its not that you hae damaged anything by testing anything other than your RO but typically you are gonna hae CRAZY readings when you put that tester in your mixed salt or especially in your tank where you hae MANY organics for that thing to pick up on; like a Koralia, for example, will alone throw that thing into orbit. For algae, get a turkey baster and squirt your rocks once a week before water changes and suck some out while still in water collum. The next day wash your mechanical filtration. Repeat, repeat