None, they only house the roots, after each mist cycle the water returns to the res via pvc plumbing which threads onto the spigot visible on the bottom of the bottom container.
This may help to clarify - the res is pictured in the foreground in one shot (black with feed / chiller lines visible), the feed lines are black and penetrate the container to connect to the manifold on one side. These are all construction pics, didn't have my return lines in place yet, they're 2" PVC.
Sorry for the hijack, just thought it appropriate given the question.
None, they only house the roots, after each mist cycle the water returns to the res via pvc plumbing which threads onto the spigot visible on the bottom of the bottom container.
Nah, I considered having the solution in the bottom of the container along with a pump, but the volume of the containers would require probably 100 gallons of nutes, instead of 15. I posted pics to clarify, after you responded.
These are my fav to use, they come in many sizes, and very strong. If you flip the lid upside down it rests a few inches inside preventing leaks. I've seen them at home depot and walmart.