In the Fish Store I work at, we simply take the tank outside (could put in garage) and fill it for 8+ hours to see if there are any leaks. Its a simple effective test to see if anything will happen. If it is going to happen, it will happen within the 8 hours of being totally full. It appears to just be a shoddy silicone cleaning job though not that its actually being pushed through. It it was pushed through by force, I don't think it would have dried like this. This really looks like they put the pieces together and just clamped them together without cleaning off the excess.