Your successful work shows the thinking model of electricity at its best !
1. Using the present pump so you didn't change the water pressure (not changing the voltage level).
2. Removing the filter and clearing debris (decreasing the electrical resistance)
3. Result is getting an increased flow of water (getting an increased flow of amperage).
Putting this in a formular you'll get ...voila ... Ohm's law.
I (amperage) = U (voltage) /R (resistance)