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Tiger Barbs need to be in a school of at least 6 but the more the better. Larger numbers will keep them from harassing tank mates. They shouldn't be kept with Angelfish because they can be nippy to slower moving fish and fish with long fins. Angels can be a tempting target. I believe the same applies to Skirt Tetras.
Denison barbs also need to be in a group of six and the minimum tank size they should be in is a 55 gallon. You need to rehome the one you have.
I can't help with Angels, but I am sure others can.
Ooh, I didn't realize the dimensions were that small.
Kelsea, you could rehome the angels and the denison shark, and up your barbs to 6 or more. If they haven't bothered the skirt tetras yet, they may not, and you may be able to keep them together. Just watch out for future nipping!
Or you could upgrade to a larger tank, keep the angels and the skirts (if they haven't bothered the angels in the past, you may be able to keep them together - again, just watch out for future nipping!), and rehome the barbs and the denison shark.