do i need to run an air pump with the Rena XP XP1.

approx 40 gallon tank using an xp1 filter. just gold fish in tank Any suggesting on filter media for goldfish?

A: You don't have a lot of options with the XP1. The setup that comes from the factory is adequate. If you have a particular water quality problem you are trying to fix then is may be time to use something else. That is why testing is so important. Adding aeration always helps so an air pump is a good idea. You can get aeration from just the filter by using the spray jet nozzle to spray the surface of the water.