well i decided that i am not going to use sand but instead cat litter as i like the look more and it being not sharp like gravel i can still get corys if i please problem is i am not sure how much to get i used a little short of 50kg of the gravel that is currently in my tank but when looking at tesco cat litter it lists it as 10 litres so not sure how much i am going to need for a 4,2,2 (ft) tank