Hello; I use a set of valves to regulate the air flow. They were made of brass but the more recent type I have seen are of plastic. I have some old brass valves that are still in use as well as the newer type.
If your pump is one of the more common types with a rubber diaphragm and simple flaps it has been best for me to be sure to not restrict the air flow too much. Closing down the valves to restrict the air flow will cause some extra pressure in the rubber parts and shorten their life. Depending on the capacity of the pump it may be necessary to bleed off some of the air to the atmosphere if the bubbles are too much in the tank. My pumps will make a notably louder noise if I restrict them too much. A gang of a few valves can do this with some extra valves not needed for the tank open just enough to bleed out the excess air. The older brass type were much easier to adjust that the new type I have sampled. I have not tried them all so there may be newer good ones out there. If the brass type can still be found they are very durable. I have some still in operation from at least the 1970's, perhaps earlier. They can be taken apart and cleaned and put back into use.
One note on air pump placement, I try to place/hang an air pump higher than the top of my tanks. It use to be that when a pump failed or the power went off, the water could siphon out of the air tubing if a pump was placed lower than the tank. I also like to hang them as this can help reduce the noise from vibration that can be boosted when they are placed on surfaces.
You may be thinking of the very fine bubbles produced by an air stone. This can be had for a while. Most air stones have worked well for me for a time and then tend to produce ever larger bubbles. I guess the channels in the stones open up with time. A new stone will fix this if the large bubbles are not to your taste.