Hi Dave,
That is a beautiful tank setup.
As for feeding, i think it would be better if you separate the current quantity of food at one sitting into 2 or 3 smaller servings a day. The food will remain fresh when you only feed what is required and also there will be less leftovers and wastage. As your axie grows bigger you can then gradually give them more per sitting.
Because frozen bloodworms are after all 'dead', they cannot remain in the water as long as live blackworms or earthworms. I generally try to remove them within 30min after feeding session. In general fresh bloodworms appear a rich 'blood' like red. Once they start going off, they turn somewhat brown and then whitish. By that time, i hope the bloodworms are long removed from the tank. How long bloodworms can last in the water without going bad is really quite multifactorial. Warmer temperatures make them go bad even faster. I would not leave them there longer than 2 hours at maximum, although i highly recommend you remove them after 30min of feeding.
Cheers.