I meant that in small tanks the amount of water movement generated by the fish moving around the tank will circulate the water more than enough to prevent there being spots of water that are completely dead. As fish move through the water they will push the water around them and help them circulate.
The venturi system should work fine lower down, so long as you have a long enough airline pipe. However the venturi will not do a great deal for oxygen levels that low down as the bubbles will not be in the water long enough for any air to exchange across the surface and the bubbles hitting the surface will give very little surface movement (I state this having compared the effect of bubbles and filter movement in my large tank - the filter wins hands down).
So essentially, it may look nice (if you like bubble walls) but will probably do less for gas exchange than having the outler pointing towards the surface. However, small tanks will rarely have oxygen concerns as smaller fish have far lower oxygen needs than larger fish (such as bala sharks) unless thye are seriously overstocked.