Hello; One way I have kept weak air pumps in operation for a while has been to raise the air stone to a higher level (not as deep) in the tank. Over time air pumps tend to become weak and not be able to push air to the bottom of a deep tank. As I live some distance from a decent fish shop I have used this method to keep some bubbles working in a tank for circulation and surface agitation. The effect will be similar to a bubbler near the bottom of a tank just a bit more unsightly.
There was a period several decades ago when all my filtration was powered by air bubbles in some manner. I also suspect that the tiny valves were made of rubber then and not silicone as they are now, so were more prone to fail.
I have also found it possible to reduce the air pump back pressure by using less restrictive air stones or just simply having an open tube end. Some air operated equipment, such as sponge filters, will work quite well without an air stone and with just the open end of an air tube. The bubbles are large but still generate flow.
Air pumps are rated for depth as well as air volume, but these generally cost a bit more.
I had an air pump grow too weak to operate my tanks a short time back. I went to the local Wal-Mart and picked up a dual outlet air pump for about $11.00. I had planned to use it until I make the 55 mile trip to Knoxville TN and pick up a good pump. To my surprise it not only operated the four pieces of equipment strongly I have had to bleed off some of the air as it was running things too strongly. Depending on the depth of your tank such a pump may work and not be as costly to buy.