I just stick the end of the hose into the turkey baster I use for spot feeding. Squeeze the bulb and then release, One pump is usually enough to get the siphon started.
A few of my friends make them out of Great stuff. It seams to work fine and cures hard. They coat it with sand before it cures and makes cool shapes. They have had no ill effects on anything in the tanks and corals grow normaly.
It's bubble. I had it in my 200 gal reef and it spreads like crazy. Try not to pop it or you will release its spores and you be picking it out for months.
My RO/DI is hooked up to a 10 gallon bin with a float switch that keeps my top off water supply full. When my sump level drops to about a gallon, my ATO turns on a pump in my RO reservoir and fills the sump back up.