Trick to adding sand while water is still in and your desire is to avoid cloudiness, is to do 3 things. Get a funnel, tube, a pipe, and a tupperware.
Make a hole in the tupperware big enough for the pipe. Silcone he pipe into the tupperware (or bulkhead it, if you desire). Drill 2 or 3 small holes around the base of the tupperware surrounding the pipe. Then about 6 along the lip of the tupperware, smaller, about 1/4 an inch from the lip, spaced evenly. Attach the hose and then the funnel.
Place the tupperware at your desired location and pour very slowly into the funnel. Have someone else pour while you hold the funnel and tupperware in separate hands. Try to avoid air getting down the line, as sand sort of likes to bubble. Not quitevlike water, but it makes amore violent displacement.
