Why are my nitrates undetectable/0?

[40custom]

So I have a 40 gallon breeder with a 20 gallon sump and I was running the tank was just one fire fish and was feeding a few pellets a day and a few mysis shrimp and was sitting around 20 to 25 ppm nitrate and then I started getting more corals and needed to start dosing to account for the lost nutrients so I decided on dosing tropic marin all for reef and ever since then my nitrates have been zero I have tried overfeeding like almost a cube a day plus little pieces of Nori as well as some from hikari and I have even turned off my protein, Skimmer and still zero nitrates, I did just test my nitrate, ammonia, nitrate, and ammonia still at zero nitrate is at .5 ppm and nitrate still at zero this has been going on for a few weeks to a few months now however my coral seems to do fine. My SPS birds nest has almost doubled in size as well as my GSP has tripled in size probably however I’m struggling to reach anything higher than zero or undetectable levels of nitrates I would say it’s the Skimmer however I had high nitrates when I only had one fish and feeding way less so is it possible The all for reef is causing a imbalance with the nitrates or is it as simple as just needing more fish or feeding more or even dosing nitrates?
Note i have a tang, two clowns, 10-15 snails, a diamond goby, fire fish, and a little shrimpy as of now and i think 9-10 medium ish frags

 

[GuppyHJD]

What test kits are you using? Are they current?
Could you take a water sample to the LFS to get a double check?

 

[40custom]

What test kits are you using? Are they current?
Could you take a water sample to the LFS to get a double check?

Good idea to take it to my lfs. I am using a red sea reef kit as well as i bought a second test kit to double check and same results

 

[Randy Holmes-Farley]

Just feed more. The all for reef is not causing a big sink for nutrients. Many tanks may need N and/or P dosed to keep desirable targets. It just means the tank organisms are using more than you feed.