If you want a more or less permanent connection try this. The OD of a 5/8" bilge hose will fit perfectly in the ID of a standard ballast fitting. Put a 1 1/2" hose clamp around the outside of your sac opening, gently tighten and your done. The OD of a 3/4" garden hose also works nicely. I have used these simple connections for my permeaent ballast for 4 seasons and have had 0 leaks or probs. The water bed fittings work, but I have found they come undone and can't imagaine they allow the same water flow.