are you trying to make a custom shape or just trying to cut costs? how big are you trying to go? sharks need a pretty good sized tank, like 300+. that is a ton of thick heavy glass. acrylic is much lighter and easy to work with as well. Weldon is the brand of glue that is used for that. either way if it was my first time building a tank, i would start a little smaller. a 300 gallon tank once it is all full of water and everything can weigh upwards of 3200 lbs. if you are just trying to make a square shaped tank just look on craigslist. you can find 55g whole setups for $100 if you are patient. i have gotten some off there for really cheap that leak but all the pains are solid. a little sealant and you are golden.