I'm trying to build an aquaponics system with PVC. I have 3" pots on 3.5" tube. When I was done with the drilling and positioning I noticed that the water just rushed below the pots, not touching them. Do I need pots that are longer or do I have to place them somewhere else while the roots are big enough to reach the bottom of the tube?
You could use a wicking system which is also known as capillary matting. Put a strand or strip of absorbent material into the root ball at planting time. Put the root ball and wick into a pot. Tease the wick so it sits in water.
Shoestrings or polyester fleece are materials that you may have in your home. Any hydroponics store should have material that lasts longer. This works best when the distance from the water to the pot is no more than a few inches.
Place a pipe in your outlet drain and cut some slits at the level you want the water to rise to. As the roots grow you can remove the pipe and drain as you are now.