Hello Rey
The bottles are cut at 7 1/2 inches. That will give the solo cup with the plant in it support from falling
over. Some plants like cucumber and tomatoes have to be tied up when then get to big.
A 70 to 120 gallon per hour submersible
pump works fine or you can use a larger one if you use a
flow control valve or just use a C clamp on the hose to slow the flow from the tank to the garden.
Ron