This is at the moment just a dream of mine... I have made a new years resolution to complete it by the end of this summer... but who am I kidding when was the last time I actually fullfilled one of my resolutions. Oh man I kill myself. Anyway the hardest part of it all would really just be mixing the concrete. Once it was completed I would paint the inside with swimming pool paint to make it water tight. I havent totally figured out how to incorperate the filtration systems, pumps, drains etc but It wouldnt be hard to figure that part out.