Currently have two angle fish in a 20g tall and am moving them into a 40g. My question is this. I am adding a light which they never use to have and also changing the substrate from standard gravel to sand. Do you think my fish will be ok with going from never having a light to having on? Also I was wondering if I could add any other fish to my tank and if so any suggestions. My angels are a bit aggressive and worry about fights. Help would be very much appreciated! Thanks in advance!