Best medium for flood and drain

So on my last grow my roots clogged my drain line so it was not able to drain properly. Normally i am mediumless but im hoping to add a medium to my system to help suspend the roots so they cant clog the drain. That being said i need to find the medium with the best drainage and minimal effects on my nutrient solution and not impeading root growth? Any ideas?

I was thinking maybe perilite

Hydroton, if it's a.flood and drain bucket system don't be scared to trim the roots.if it's a tray system they should air prune.