The smaller plecos shouldn't do any damage to your plants. My BN pleco doesn't even bother getting any algae off my plants, it sticks to the driftwood.
Sand wouldn't necessarily make it easier for plants to root more easily. I found that plants were uprooted much more easily using sand, unless they had already developed a good root system. Gravel is more porous, which gives more room for roots to easily grow. When sand starts compacting, it's a bit more difficult for roots to push through. |