Siphon, as in to remove water for a change? Or to remove detritus?
Either way--a chunk of tube long enough to allow you some moving room and reach a drain or a bucket. Fill the tube up with water, cover both end, submerge one end in the tank and the other in the drain or bucket, and uncover the ends. Use the tip to gentle clean low flow areas--hovering just above the area is usually sufficient to pick up detritus without sucking up a bunch of sand. I use .5 ID tubing.