DIY Overhead filter

[Oughtsix]

I doubt you will see an appreciable difference between lava rock and scrubbies as a wet/dry filter media. I would choose which ever worked best for your design.

Either should be more efficient than submerged media.

The trick will be to wet all the media equally instead of having just a few paths in which the water flows through the media. Your spray bar / trickle plate will be key to the efficiency of the filter. The more effective they are at breaking the streams of water down to drops the more efficient your filter will be.

 

[TexasMFK31]

I would do the plastic scrubbies for your OH sump with a tray to drip into them. The scrubbies won't channel like the lava rock would and are lighter. The drip plate will disperse the water evenly over them all.