I have a sump, the problem is out gassing of CO2 - which is the only real problem with them. I removed the trickle plate, but I left in the bioballs in and try to keep the water level relatively high.
If you can seal the sump you don't have to worry, it works almost like a giant CO2 reactor as long as it is a closed system. I did it with saran wrap, just to see if it would work before I got into building a cover a drilling holes in in for filters etc, and it works great. My CO2 levels stay pretty constant- so much so that I just left the saran wrap. Piece a cake.
The plural of anecdote is not data