i think a liter ways 1kg so 60k if your worried about putting a fish tank upstairs i have a 100g in my room which is upstairs with rocks and sand it wouldn't surprise me if it weighed 500kg but i checked with a building person to check my floor could take it
A litre of water weighs a kilogram so a 60l tank would weigh 60Kg plus the weight of the tank (2 or 3 Kg) plus the weight of the gravel, sand, stones and filter.