yeah if not planted get the thinest layer possable, easyer to clean up.
And if your using plastic plants...your lfs should sell these lil suction cups that are made for your airhoses or to keep some bubble walls mounted down, get a few. Cuase these suctioncups has lil holes on the top that plastic plants will fit after you pull out there lil gravel joints, so now your plants will be suction cuped down to the glass so you wont worry about having too thin of a layer gravel.