go to your local boat shop. 3/4" bilge hose. Very easy to work with. Don't use it with reversible system though, it can handle pressure but not vacuum.
Flow-rite IMHO is the best there is, reinforced like Spa hose, but much more flexible and black in color. It works with the Fly High quick disconnects as well.
I like spaflex, but it's really difficult to work with. I saw some stuff in the pond dept in Lowe's or HD the other day that looked promising. $1/ft, and looked a lot easier to stretch over a barb fitting.