New API Test Kit and Algae

I was getting green algae on my sand so I got a new API test kit today and tested the phosphates of RO water from Walmart and Giant Food Store and I got a reading of close to 0.5. Then I tested my tank and I got 0 which would make send if I have algae on my sand it is absorbing the phosphates. If I get a RODI unit do I have to replace my pull out faucet. I dont understand why both companies waters would get the same readings? Both companies are from different manufacturing plants.

 

Unreliable methods of RO/DI... They probably do a bagillion gallons at a time (lol) and go as long as they can on there filter media. I use a RO/DI unit on my system and I still need a phos reactor (awesome little device). The best way for me to attach it was to add a splitter to my washing machine water line (similar to what you would put on a hose feed outside to run two hoses from one line) and taped in there. GOOD LUCK MY FRIEND! Let me know if I can help anymore.