no nitrates

So I picked up an apex to better track my tanks stats. I am running the ORP probe and reading around 170-192 throughout a full 24 hour period. My nitrates have not been tested in over week but they were 0 the last time with my skimmer running 24/7. i have a new tester arriving since i ran out...

I have had a decently bad algae bloom because my nitrates got to low "for me" they got all the way down to 5ppm for my tank which is usually at 20-30ppm. Some corals are fine but some have been closed up. Would i get any problems if I dose nitrates to quickly?

My Fluval 13.5 is running consistently at the following numbers now for two weeks. Is this a problem, and do I have an in incoming Dyno issue? I have 3 fish, and a mixed softy/LPS reef set up (no SPS). no Ammonia/Nitrites (check once per week) Salinity 1.025-1.026 (refractometer) PH 8.4 -...