fishroom build and 800 gallon tropical pond

Hi, i used stainless steel brick ties linked together in layers to reinforce the concrete i thought that should be enough as all the walls have support against the brick walls and the front is supported by 3x2's and 18mm chipboard which i treated. I planned this for months before moving i measured the garage when viewing the house then designed the pond on 3d studio max on the laptop, i did 24 designs of paludariums, plywood tanks and ponds and worked out what fit and prices and this was actually my second choice but i think its worked out better because my other idea didnt have an overflow. I got the liquid rubber from 5playleisure.co.uk and is the cheapest per litre anywhere i checked everywhere, cheaper than fibreglass and epoxy for coverage plus liquid rubber is the best choice for concrete because over time the cement may get tiny cracks but the rubber will stretch but epoxy is brittle and will crack.il start putting the prices and store of the stuff i get, the cement was from b&q at £4.15 for 25kg on multibuy but usually its £5.90 and the cheapest near where i live. The ballast was £1.23 for 25kg but i would advise a tonne bag for £40 i spent a bit more than that on single bags.