Nitrate problem after water change

[JCortez3]

Hi I've had a biocube 32 set up for about a year and when I thought I had no nitrates with my API test kit I bought a salifert test kit and found my nitrates to be over 100ppm.

Well over the summer I dealt with a GHA issue and weekly water changes my test still kept coming back at 100ppm for nitrates.

Now I removed all the rock yesterday and swished around in fresh saltwater and vacuumed all the sand and started with new salt fritz rpm (used to use reef crystals) anyway tested everything again this morning and found nitrates still over 100ppm. (Did a 10g water change)

Alk-12
Phosp.-0
Ph-8.0
Calcium-480

All my corals look good and softies and lps and only have a diamond goby and damsel but my candy cane not looking good.

Anyway long story short I'm trying to find how to get rid of these high nitrates ( I use a RO buddy for RODI and have a v2 biocube skimmer, carbon and filter floss for filtration and like I said doing weekly 5g water changes. I am also not having GHA anymore after a while back using phosphate RX to kill it and manually remove it. Any help appreciated. Those parameters were as of today 10-4-20

 

[lapin]

Have you had your LFS test your water?
Also have you tested the RO water?

 

[JCortez3]

I haven't had my LFS check it but I have tested it for phosphate and nitrate and both are 0.

my worry is that either a test kit is bad or because of the little bit of GHA left I'm getting a false reading.