That is one big water fall!! I would echo the suggestion to buy a pump made for outdoor fountains. They have a lot more power and are made for pushing water that high. Also, I have found that most of the output areas on the pumps require 1/2" fittings. I would stick with 1/2" tubing. It can be a bit tricky to get it to go where you want it, but for a 24" water fall, 1/4" tubing may not give you the flow you want.