The air pump powered tetra whisper is the one I refer to when I just type "whisper" I call the others "i#-#".
You can get a cute little Fluval Edge pre-filter sponge for a couple bucks.
Slip this sponge just far enough onto the bottom of the whisper so that you can no longer see the contraption at the bottom but can see the lifting pipe.
Yes, when I say lift pipe I refer to bubble operated water raising pipes.
On gravel thickness:
The point of gravel in an un-planted tank is to act more like a door-mat in catching debris from the tank flow and holding them until you siphon them out. This requires about three layers of gravel. So depending on your rock size your "three layers" could be as little as a quarter inch or as much as an inch if you're using nice small river stones instead of gravel.
If you have too much gravel you won't be able to extract all the "flow" your little one puts in the tank and you will get stagnant water down in it since we try to keep the circulation of the tank low. The only exception is with actual planted tanks which need a minimum of one inch of bottom and the more coarse the gravel the thicker the bottom needs to be. You CAN do "planting areas" with finer crushed gravel then use coarser gravel elsewhere thus maintaining the 3 layer rule and still having sufficient inch thickness.
... you CAN actually use a prepared door-mat for tank bottom, it just has to be one of those plastic grass looking ones, cut it so it is about an eighth inch in from all sides so the edges don't make pockets on the sealant.