First things first so you dont forget go to austal insulation in Malaga and get some free styrofoam skins ( I would go 20mm thick might take afew skins)
Next build a stand that is flat,level and ofcourse will support the weight (if you need some advice feel free to ask) then I would add a. 20mm marine ply board ontop of the stand for the foam to sit on
Third get a piece of glass cut that is more then big enough to cover the whole crack I'd cut it the internal width of your tank and atleast the same thickness as your tanks bottom. Make sure you have the correct silicone not just any bathroom silicone ( I don't have any left and can't remember what it's called think its. V10 or something like that)
Fourth would be to put plenty of silicone on the patch piece and I mean alot !! When you put it in place and rub it in you don't want any air bubbles under it. Once you have done that put a nice thick bead all the way around the edge of the patch piece I use my finger to give a nice round... While your at it better off re silicone the hole tank aswell .Let cure for a minimum of 48 hours but the longer the better
Last thing is to lay a old thin bed sheet (I find light blue works good ) over the stand with the foam on then position the tank on top fill roughly 1/3 or 1/2 way and let sit for a couple hours . If there is a leak you should see the sheet is wet as there will be a dark patch. If no leak keep repeating this process until full and then I would leave it full for a week or so just to be safe if all good drain the tank put into position in your house and hope to god you will never have the thought " I knew I should have just bought a new tank" lol
Edited by Bickley, 11 June 2013 - 08:37 PM.