I had 2 emeralds in my 45... I loved them - they became very active during the day and were quite fun to watch. Altho I never saw a problem with the emeralds and the hermits, etc., I did have a problem with the emeralds and the FISH. In fact, one of them bit a fin off my toby puffer!
Thank goodness the puffer was healthy and recouped --- the emeralds went to a local LFS...
Deb