Simonas, your rock is same kinda layout as mine, the arch
and mine is identical tank mostly (Kent Marine 94L) and my layout is cool! Its a little more complicated but its more mature than yours and i can mess around with mine every day if i wanted lol.
I gravel clean mine as i hate my sand being anything other than white
but any dust that settles behind rocks, even in that settup can be reached by blasting with turkey baster if needed! (which is worth donig to stop it building up behind rocks).
Its also great scape for corals because of the flow... lower flow or higher light at the top, stuff like gorgonia does awesome on the left as thats where the flow ends up and zoas/polyps grow great on right with flow gonig slightly over them.. and mushies etc in the middle so they get food without being blasted flat accross tank.
Great scape! Cant wait to see more!