another thing i heard was not to use a hanna checker as its not meant for fresh water and the readings could be completely wrong. i havent tried testing a fresh batch of saltwater mix. i have also used the salifert test kit and its reading 0 for rodi water o for tank water??? im not sure how accurate that kit is.

You definitely should have a TDS meter. Get the one that tests your water before and after your DI canister.

I don't see the size of your tank, but 2 tablespoons of GFO would be way too little unless the tank is a small nano.

If your nitrates are truly 0 with a reliable test kit you could dose amino acids to bring your nitrates up without raising PO4. This will allow you the remove PO4 biologically if your system has become nitrate limited.

by definition, an RO unit should strip everything out of the water. If you are testing your RO water and it has PO4 et al then your RO unit is not working. The only real way to test your RO unit is with a TDS meter. You can get one and put it into your BRS system. If you have anything other than 0.00 then your membrane etc may need replacing.

I have BRS 5 stage 150GPD RO/DI unit with the inline TDS meter, and it is 0.00 before DI and 0.00 after DI. How long have you had your RO unit? if it doesn't have a flush value, the life of the membrane can be substantially reduced with regular use.

I know Calgary's water is relatively hard, on average in my area I have seen it as high as 175ppm before going through a water softener, after my water softener I have 10-20 ppm on the TDS going into my RO unit. However; it sure is 0.00 on the way out.

My rodi unit is four months old but I only started using it late December 2013

Surrey
 

Hey, I live In newton and I just use one of those API tapwater filters and my water tests 0ppm always. There's something else going on.

The brs calculator says 18 tablespoon of regular gfo for a 75 gallon so 2 isn't enough . Water quality this time of year is bad due to the runoff , here in Edmonton I tested tds of 340 ppm the other day but im still getting 0ppm out of my rodi unit so I don't think that's your problem.