Surface tension is like gravity; it is the force of the water trying to stick together. A bubble has two forces. The force of the air on the inside is trying to get out and the surface tension of the water trying to hold everything together. These bubbles will only last as long as the two forces are equal. Some chemicals (like melafix or pimafix) affect surface tension and cause the bubbles to break. Most water bubbles fail due to evaporation and / or high surface tension. The normal tension of water is 72 dynes/cm at 25°C. However pure water (DI, RO and distilled) is higher due to the better bonds between hydrogen ions. Also these bonds will increase if you have hardness due to mineral salts.

So if you want more and better bubbles, use soft acid water and protect your nest from evaporation by insulating it from any nearby heat source (light bulb) with 1/3 of a white Styrofoam coffee cup.