air toys only add O2 when they breack the surface of the water. there is too little surface area, on the bubbles, to allow more thean trace exchange of O2 as they rise.
they are little more than decorations and havng your filter disturbe the surfcae gives far more O2 exchange.
the down side of using an air toy to disrupt the surface is, a big increase in evaporation,
even so i love my air stone, air curtain and air disc and leave them on 24/7. but the fish are just as happy if they are off.