i would say a better tank for a peacock is a 30 or 33 cube, get enough sand to get about a 2-3" base and get enough LR on the bottom where it almost covers all of it and it can make a good burrow system, mine in her 33G cube has made a burrow with 5-6 ways to get in and out, she feels more secure in an area with more rock, when she was in a 40G breeder by herself and only 2 pieces of rock she would not leave her burrow, now she is alot more active and i can tell she feels more secure, she might be giving me some molting behavior right now so i am leaving her be
lighting...i would go 1W per gallon MAX they are sensative to light and hate bright lights, light that doesnt penetrate the water very much is very good, such as flouresents with no reflector of PC lights with a white reflector, if you want your peacock to make a burrow in a specific spot start to make a burrow in that spot for it, make a cave or start to dig out a spot where you want it and i would almost guarentee thats where it will make its burrow