Yeah the crack can be repaired so the tank is functional. Are you able to rotate the tank so that specific panel can at least be used as the "back" panel? Regardless, you would score each end of the crack with a drill. Which would help prevent the crack from expanding. Then you can fill the crack with weld on. You can then also weld on another patch of acrylic over the crack to be safe. But you might be able to get away with just the first step since it's a smaller tank.