Bioballs vs LR rubble in Sump.

[Todd]

I understand that Bioballs when used in a wet/dry type system can contribute to nitrates due to accumulation of detritus.

However if Bioballs were added to a sump in a relatively detritus free area, what difference would this be from adding LR rubble in an attempt to provide an area for beneficial bacteria to colonize?

I have been unable to think of a good reason, yet notice that there is little use of bioballs in reef tanks. Could someone enlighten me as to why they are not used in this manner?