Hey JSL,
A 375 is a good size tank for multiple large angels. I am currently planning a min. 375g tank for my basement in which I will transplanting my 9+" emperor, 9" Blueface, and 6" queen (along with all my other fish in my signiture).
I am planning on adding a couple more angels in the mix as well once the tank is established for a few months and I get all the kinks out.
Key with adding multiple angels is the following:
- Different species is key. My emperor definitely pays more attention to the Blueface, but since they have been together for so long it is a grunt here and a grunt there.
- Different colors - many people add juvis because they are small. As you know, most all large angel juvies are similar in color and close in shape. IME, if you want different angels, add them at various stages of growth. I would say no larger than 5" (due to diet in the wild. Larger angels are harder to get to eat in home aquaria because of their feeding habits in the wild).
- Different sizes - along with the coloration difference, the sizes need to be different as well. When I added my blueface and my original french angel they were larger (by 2+") than my emperor. I did this due to the fact that I knew that the emperor was going to be the most aggressive. When I added my Queen. She was half the size of the emperor.
- Lots of hiding space - this is the key concept. When you add a new angel, it is advised to take the LR out and re-arrange so that the personal "spaces" of the established angels is disturbed.
- Feeding - make sure that your angels are eating EVERYTHING! Many times the larger of the angels will eat first (much like a male lion in a pride). If you add an angel that selectively eats or is timid to get in there and "fight" for thier meal, they will be in trouble.
- Food - you need to have a wide variety of food for your angels. Currently, my fish eat flake, pellets, frozen meaty and veggie cubes (sponge included), seaweed, silversides, and frozen krill. As a treat a few times a week I feed the tank PE M.Y.S.I.S. All my food is soaked in Vitachem and Garlic.
- Water quality - almost reef-like conditions. I have never had over 10ppm. I can quickly tell when the water needs changing because the emperor shows stress spots when something needs adjustment.