Ventrui Valve - Should I Have Bubbles?

[Colonel Mustard]

I have a Fluval 4 filter unit and it has the option to let air into the filter nozzle exit and this adds bubbles to the water. I have read a couple of things - some say you don't want to add too much oxygen others that air bubbles are helpful. Can anyone advise on what is the best setting?

I have

Platys
Guppies
Tetras
2x Dwarf Gourami

 

[Majjie]

Bubbles aren't necessary for the fish (although some like to play in them) and they tend to be bad for plants - if you have real ones.
I used to adjust my outlet to produce bubbles - because I liked them - but then I got more into plants and so now I don't have any bubbles.