Stick some filter floss/filter foam to get the larger bits of dirt first off.
bio balls or whatever are great for gathering nitrifying bacteria but are not good to get the large bits of waste.
I have had a couple of jumping fish in the past that jumped into the trickle filter and fell all the way through all the bio balls to the bottom of the bio ball chamber (I have an Aqua Medic Anthias 120) - so we had to take all the filter balls out to get the fish back. They were all fine and acted completely normally when added back in the tank. So the foam/floss pads will prevent that happning.