Making a case as to why NOT to bring home a Regal angel

[i have crabs]

ouch,
anyway, if you had a bacterial infection bad enough to kill a bunch of fish something else must be wrong sine bacterial infections and similar issues usually are caused by problems with the water or the fish's immune system, id do some checking into the usual amonia,nitrite,nitarte test's maybe ph,and alk if all thats good maybe look at what your feeding