What is resistance for a pump?
Head: This is the vertical distance between the water level and the highest point to which the water is pumped.
Tip: If the pump is on the pond floor, you do not need to count the distance between the pump and the water surface as the head !
Hose resistance: water flowing through a hose experiences frictional resistance, the narrower the hose is, the more resistance; the capacity of a pump decreases with increasing resistance.
Choose reinforced spiral hose with a smooth inner surface and a diameter corresponding to the largest connection size of the hose coupling supplied with the pond pump.