If it is a tank manufactured by a company that makes tanks, it will be better. Some tanks are home made by beginners and you don't want to buy someone else's problem. Even manufactured tank will have problems as they age and get mishandled. Most manufactured tank are flame polished. The flaming process weaken the acrylic and eventually you get this white thing in between the joints and stress fractures. That white thing is a separation of the joint. That is not good. It may not fail until a long time but I would not feel comfortable with that. You can repair it by laying the tank with the bad seam facing up and add the solvent to reseal it. It will fill the separation. The seam will be still white but will look not as white. But, don't get extra solvent on the tank surface. It will create more stress fractures with the solvent once it contacts any surface that been flamed polished. Good Luck.