From what i remember for the hoses i bought years ago, they were maybe 8"?
You can work it out though, use a rod and put it in the pickup hole till it touches the bottom. Measure this amount and work out how far the elbow goes into the tank with the groment, then work out how long the pickup filter/one way valve is, that is how long the tube should be.
If you don't have the filter/one way valve, you will need to go say 1/2" shorter so it doesn't suck its self to the bottom of the tank.
