So far it is fine, got a good bead of silicone 1 all the way around the seam. I am going to let it dry for a couple of days and fill it up to see if it leaks then I will let you know how it goes.
And also a 40 breeder is not just for reptiles, it is actually made to hold water. The wide and short dimensions give it more floor space for cover oriented fish enabling the fry and females to not be harassed by the dominant male.