i recently have gotten a 20 gallon tank that has a red tail shark already in it he is probably about 2-3 inchs long and has been alone in the tank for about 2 years, i then put in a jeweled cichlid who is about 1 inch long just yesterday and they seem odd.. they sometimes will nip at each other and sometimes just swim by, ive also notice a chunk missing out of the red tail sharks fin, i was wondering if this is normal and they are feeling each other out or if i should separate them?? also will the fin grow back??