I can't tell you for sure and neither can anyone else on this forum unless they are able to survey your house, but the current building regulations (providing your joists are in good condition and floor boards etc) are 1.5KN/m[sup]2[/sup] which is 152.9 Kg/m[sup]2[/sup] a tank of 1.2*0.6M in footprint dimension has an area of 0.72m[sup]2[/sup] so inputting this figure into the equation we get:
152.9*0.72= 110Kg, the tank alone is going to weigh in the region of 40Kg so you'd no way near be able to fill it safely over an area of 1.2m*0.6m to current building regs, chances are your house is older though when things were built to a higher standard.
You could also put a thick piece of plywood under the tank, for example you could spread the mass over an area of 1.2m*2.4m, which is 2.88m[sup]2[/sup], which if we reapply the previous equation:
152.9*2.88= 440Kg
Take away the mass of the tank and stand and you're probably left with 370Kg to play with, which would probably fill the tank 3/4 of the way up after substrate/decor etc.
There's a possibility that over an area of 2.4m*1.2m it may be absolutely fine, but it's impossible to say without the opinion of a structural engineer.
