The best way i have found is to do what jw said and use a pvc pipe...but, get your sand wet before. there will be a lot less, if none, "smoke" dust when you pull the pipe out. add it slow. i have a 2 foot pipe and stick it in the tank all the way down to the current sand bed and fill the pipe about 1/2 way (estimate) and the raise the pipe up a little and let the sand kind of sift out. you can drag the pipe to the left and right when you do this to spread the sand around.