Ed wrote...

And what would build up that the plants couldn't use?

Everything the plants couldn't use.

In any case it would be easy to "flush out" the space beneath the
plate if one modified the risers to allow for that.

Sure. That would work. But if the risers are there, and the plates are
there, why not use them? I use both UGF and mechanical filtration on my big
tanks. Works great. I recommend it.

kush

"You can't have everything - where would you put it?"