I have a shoal of Rummys with my Angels, just make sure you get good sized Rummys. IMO they are the best shoaling tetra. They are very water sensitive though and take your time to introduce, i lost 2 when i first got mine, i just did the normal 1 hour acclimatisation, try to take your time acclimatising them, maybe give them a couple of hours slowly introducing your water into the bag.