RO Water TDS levels? Too low bad for fish?!?

You could dilute by a factor of 10 or 100 then multiply your results.

 

GIve that man an 'A' in chemistry. K+

 

Thanks for all the info everyone!!! Definately puts my mind at ease!!

 

Your salt mix supplies the TDS (minerals and elements) that are required. Your goal is to provide as nearly pure wate ras possible so you get the correct elements in the correct amounts as supplied by the salt.

A good reef quality RO/DI unit should give you 0 TDS no matter what the incoming or tap water TDS. Contrary to popular belief, changing filters ahas very little to absolutely no effect on final TDS. That is the job of the RO membrane and the DI resin, not the prefilter and carbon which are there to protect the membrane which does 98% of the work. You change the prefilter and carbon at 6 month intervals regardless of final TDS. You change the DI resin or cartridge at the first signs of anything other than 0-1 TDS on a consistent basis and you change the RO membrane when you find DI resin is not lasting as it should, usually at 94-96% rejection for me. The dual inline TDS meter should give you an idea how well the membrane is working with its first probe and how well the DI resin is working with the second probe. RO by itself should be removing TDS by a factor of 10 or better and the DI should read 0 TDS.

New saltwater TDS is way above the range of a TDS meter which usually only reads to 1000 ppm. Some meters will read to 10,000 ppm by tenths but NSW is going to be in the 35,000 to 60,000 range, even diluted it would be tough to read and certainly wouldn't be accurate. It wouldn't tell you much either since you have no idea whet the TDS is made up of, only that it is electrically conductive.