Very new to this stuff so forgive me if these questions have been asked before.We are building a large tank 2.5meters x 1.5 meters x 1.5 meters to take a salt water fill. The weight of the water will be in the region of 6 tons. The frame supporting this tank is made from 6" hollow box section stainless steel, the walls and base from 70mm clear cast acrylic sheet. So the question is how do we seal the corners ? The acrylic is supported by the frame with a gaps that we hope to fill with silicon sealant (which one??) to seal and allow for thermal expansion. The sealant is critical and we have done some bench tests to find a suitable one without much luck as all fail in tension so presumably the design should allow for the silicone to be in compression to work...As you can tell there are lots of questions to ask, any help and advice from you 'Guys' will be very much appreicated.