The fish expert would be incorrect. Fritz complete is a detoxifyer of ammonia, nitrite, chlorine, chloramine and heavy metals but it does not supply the nitrifying bacteria that we are trying to establish. (
https://fritzaquatics.com/products/fritz-complete )
Fritzyme #7 and Fritz turbostart 700 (
https://fritzaquatics.com/products/...ical-additives/freshwater-nitrifying-bacteria) are live nitrifying bacteria cultures so you can add fish to a tank immediately when using these 2 products. The key is not to overload the tank even when using these products because the bacteria colony will still need to move into their "home" ( the most highly oxygenated areas of the tank) then process the ammonia the fish will be producing in order to reproduce and enlarge the colony. If there are no fish, there is the fritzyme trace that has elements that feed the nitrifying bacteria.
As for your test results, I don't trust them. In a cycled tank, there is a nitrate level unless you have products or plants that are absorbing the nitrates as fast as they are being produced. It makes no sense if you used the Fritzyme #7 and still not getting a nitrate reading. It doesn't matter what testing material you use, the end result is nitrate. No nitrates means there's nothing in the tank that is producing them if there are no nitrate consumers in the tank. If you used the fritzyme #7 according to the directions, you have nitrate producers in the aquarium.