Would this be okay for my gerbils?

At the moment they live in a tank but there isn't enough substrate in there to allow for burrowing. They have a bottle attatched to the side of the tank and are fed from a bowl. The gerbils are around 1 and a half years old. Would they cope okay if I removed the bottle and food bowl and filled the tank with enough substrate to allow for burrowing (most of the tank will be filled leaving a gap at the top for them to run) and i left the bottle on top of the tank with the spout poking through for them to drink from? I would have to remove the bowl and ter feed them also, would they be okay with this sudden change?