I don't know a whole lot about dwc systems, but my general understanding is a little betterr than yours, so here goes...

Air pumps only pump air. Their purpose is to make sure that your nutrient solution is well aerated - full of millions of tiny air bubbles. Your roots need air just as much as they need water, hence, the air pumps. The air pump attaches to air stones - bubble makers. You have air stones in your individual buckets as well as in your reservoir. The aeration is a vital part of the hydroponic process.

To move water/nute solution, you use a water pump, and gravity.

Memorize the above and you'll know as much as I do about dwc systems. Dayum, it just occurred to me that, if you then learn one more thing, you'll be smarter than me. ...that sucks.

Good luck with your grow! :thumbsup:

PC :smokin: