Live rubble in sump

[Jason2000]

My fluval evo 13.5g has a three part sump with skimmer,filter media,heater/return pump. Because the nano skimmer only occupies the top half of its section there's a void below which I'm considering filling with live rock rubble to aid biological filtration. However as its pretty much the first section the incoming water hits i'm worried it will be a dirt trap, which won't get washed as filter media would. Will this cause more problems than its worth? 

Be glad of any opinions 🙂

[Brianr24]

I would put pond matrix in there. U can put it in a mesh sack that you can take out every so often and rinse in old saltwater when doing water changes.

[Clown79]

Rubble will prevent being able to clean the back chambers which should be done regularly.

 

Putting it in a media bag will help with being able to clean it.

[Subsea]

Seed sump with copepods.  Let pods live in detritus.

[mcarroll]

I'd keep it empty, personally.  If you put something down there I'd heed @Clown79's advice to put it in a bag (or something) to make it easy to remove for cleaning.

 

But empty is better...plus you shouldn't need any extra media.