Yes, the nanno WILL process some ammonia and that is why my fry tanks were lit up 24/7 to aid the process.
I would NEVER add Instar I nauplii to a fry tank because they have a tough carapace that is extremely hard for the fry to digest, as well as they don't have the needed DHA component in their egg sack but will have it if you enrich them first with Dan's Feed.
I had good yields with decapped but for me, I found it easier to separate the nauplii from more of the crap when I merely sterilized them. Decapping seemed to leave a lot of crap in suspension with the nauplii. When sterilizing I don't do it until there is ANY colour change, just a few minutes with bleach and then do the rinse and place in hatching container.
I never use nanno for Nauplii unless it's just to grow them out. I leave them in the hatching container so it's about 24 hours to mostly hatched, and another 24 hours to reach Instar II stage, and then I enrich. (total 48 hrs in hatching container, no food or enrichment)
When enriching, I use new water and enrichment after the first 12 hours as the enrichment in the water promotes nasty bacterial growth so I'm reducing the problem when I renew the water and enrichment. I also SEEMED to have lower yields back when I used to go a straight 24hrs with NO change and I think it's because in time, the enrichment seems to coat the nauplii, killing them off. I could see the apparent coating under the microscope after they were in the enrichment for about 14-16 hrs.
I'm just an average seahorse keeper that has been at it a bit longer than some but when it comes to brine shrimp, I've been at it for about 25 yrs. I used to sell to some of the local stores around me so I was raising them on a large scale.
My brine shrimp page hasn't been updated in a long time now as I'm getting to old to figure out how to make some types of changes but it can give you some idea of what is involved in raising brine shrimp to adult if you wish to try. I did it because here in Canada we don't have a source to buy live adult artemia.