Not the best build quality. This usually happens when the glass is not cleaned thoroughly or the silicone has skinned a bit before placement of the glass. I wouldn't be to concerned about the particular seam in the photo its not that bad but you have a photo of it now so just keep and eye on it from time to time and compare to see if its getting worse. If I had to bet on it I would say its not likely to get worse anytime soon (meaning years). I would have no issue using this tank whatsoever.
Added: if you don't need the tank right away and they will exchange it then I would go that route but either way I would say that tank is safe to use without a doubt.
Last edited by Dman911; 06-05-2017 at 07:13 PM.