Thanks for sharig. That blue-line looks great along with your other large angels.With your QT method, it should pose little risk to introduce diseases. I wouldn't want one new fish to take out what I have in the DT either!
I can't see what they are nimbling on the tank floor. From your description, it seems like pellets they are picking off the bottom - if you don't have some yet, you can try the bigger 3mm NLS pellets too since your pellets seems small - 1mm?