Need some clarifications! :)

Hi there - noob here

I've got a bubbleponic system with an air pump. I'm wondering a few things..
1) Why should I not submerge roots completely in water?
2) Do I ever need to change water? (not add, but get new) (I add nutrients already)
3) Should I leave the air pump on 24/7? Can I do it hourly?

Thanks!!

1) You can let them submerge completely. So long as you supplement enough o2 why would it matter?
2) No you don't, you can simply add back if you choose to. Maybe change on the switch from veg to flower if you like, i never bother myself.
3) You can if you like... also no problem to switch off the pump for a several hours per day if you choose to. hourly?

switching off the pump would depend on res size and temperature. Bigger, colder res will hold more oxygen. If you don't want to run it continuously, I would get a timer and run it something like 5 min on, 5 min off, or similar. I wouldn't let the res sit for more than an hour without bubbles.

A lot of people don't change the water. People who do seem to get better yields. Not changing wont kill or make your plants sick, but changing the water helps ensure the proper concentration of nutes, and also helps to remove salt buildups. If money is a factor you can get away with fewer res changes, but if the only factor is laziness, then that is not acceptable. There are some people who use beneficial microbes and they don't like to change the entire res at once, since they would be dumping their bennies.

Leaving some of the roots dangle in the air is a personal preference. If you have a weak air pump it is prolly a good idea, as long as the pump makes enough bubbles to splash water onto the roots. If you have a really strong pump it is probably unnecessary. The exception would be people who are prone to root problems, sometimes a pocket of air can help keep disease away.