Cycle question!!

[Whatigot]

I was advised against a plenum by everyone, but by noone who had tried.
I'm actually setting up a 90 gallon reef right noe with a plenum because it seems like all the books I read suggest that it is an excellent system that requires very little maintenance.
As I understand it you need to think about changing or seriously cleaning the overlaying substrate avery 24 months or so....
It seems like there are a lot of hobbyists to don't reccomend it but very very few who have actuallhy tried it.
I have read that you need to be careful about how much rock/sand you are using as too much will result in too much dentirification and nitrification.
seems like everything else in this hobby and requires some measure of planning and adjustment.
I am looking foreward to seeing for myself how it works.