Air stone location and bubble size question

Hi all,

I have a question regarding aeration, on a 45 gallon tank I have two flat
air stones, and for the sake of cosmetics I decided to hide them under the
gravel bed, behind some decorations. Now all if fine except that the air
bubbles since they have to merge between the gravel are much larger as they
surface.

My question is, if that is acceptable or are there any negatives associated
with such practice, putting airstones under the gravel. The fish seem to
like it, they ride some of the bubbles to the surface, and the visual effect
is not so bad... instead of the fine fizzle I have larger bubbles. Surface
agitation also seems increased.

Any comments are greatly appreciated as always.

Kind regards.

Steve