Two of the new primes can definitely work over a 40 for a mixed tank. You can buy used ones, make sure they’re the 16’s, and you might have enough leftover for a t5 fixture to supplement them. You’ll notice in my 65 that much SPS are in the top portion of the tank and I even have some growing in the middle. I have 3 over mine but one of them is a first generation AI I’ve had for years. The good thing about 40’s is they don’t have a middle brace over the top so you can play around better with the light distribution. My 65 has a brace through the middle which is why my lights look offset.Do you think I could get away with 2 in a 40 breeder?