The most important thing to remember when considering your pump...is the fact that around 70-80% of the volume of your system will be used up by the grow medium!

For instance...my grow try takes 7-8 minutes to fill [ WITHOUT anything inside it].When the tray is FULL of clay balls..it takes just under 2 minutes to fill!

I'm using a 6 watt pump for about 30 litres of grow tray.

A smalll pump will easily feed a small grow.

Think about the total volume of your system then subtract 70% of it's volume then rethink!

My pump cost me only 10£