Could TDS be zero?

[rjs5134]

I have a spectra-pure RO/DI(25gal/day) and an in-line HM Digital DM-1 TDS Meter. It reads 249ppm on the supply side and zero on the product side. Other posts seem to be happy with .03-.01, is that 3ppm-1ppm or .03ppm-.01ppm? Most TDS meters measure in 1ppm intervals. I have calibrated it using the solution provided, should I be shocked with 0ppm reading?

[Reefland]

No you should not be surprised. A good unit with good membranes and resin will produce 0ppm.

[The R/C Man]

I also read 0 TDS....

[rjs5134]

Cool,
Thanks guys, still trying to figure out the cyano bloom. Note to self, Scratch off RO/DI.

[golfish]

The TDS meters that come with RO units are better used as a guide line to let you know when the membrane needs replacing, their not very accurate..Even the best RO mebranes can only remove 99%...your DI is what's getting the rest...Although I test my RO water for TDS (just as a guide line) I don't bother testing the TDS off the DI, its always zero on my TDS. I use a Hannah PO4 Colorimeter to test the DI water, this gives me a much better idea when my DI resin is shot. I've seen the PO4's as high as 0.10 off my DI..that's when I've had my worst alage problems.

FWIW, PO4 test kits have proven to be worthless for me.

[The R/C Man]

Just as a quick note: Cyno grows in the presence of nutrients. Sovle your nurient problem and the cyno will go away. typically its from over feeding and or lack of skimming.

[rjs5134]

Probably lack of skimming, my skimmer sucks and will be replaced shortly. Definately not overfeeding, I only have 2 perculas and a snowflake eel and recently noticed one clown was on the skinny side.