@vetteguy53081 First, I want to say thanks for all the help over the last several months as I found this website. No on tap, I have 7+ stage set up.
Agreed on speed. I think in the back of my mind the system could handle it. I should share that I have a RSMax500 that is >4 years old. I had put about 10 pounds of ceramic biomedia that I had in that system for a long time that I place in the sump in this set up (still there) to help, in conjunction with the live rock, jump start and digest the ammonia.
When I dark cured this tank I had significant bio die off that drove my ammonia to >2.5 for about 5 days, then it came straight down to .02-.03. I am using Hanna and there is a .05 +/- margin of error. To me .02 = 0 with that type of spread. Any tank I test with my tester, using that tester, is never zero (debating about getting a Seneye to prove this theory out, other testers read zero that I have used).
With all that said, I did have a 36 hour spike, or I think. My Hanna read .70 one day after adding 3 fish in 2 days. 18 hours later it was .30 then 24 hours later .02.
I can shift to water changes every 2 days if that would help.
Phosphates have been a struggle in this tank. My others are right inline at .04-.06. I am deploying all the same exact tactics but just haven't been successful yet.
The low O2 is very interesting. Air stone?