I modified mine by drilling a small hole in the cap on the collection cup then dropped an airstone down into the main body of the skimmer. Now it produces more bubbles. Just make sure you put a regulator on the airstone and use that as adjustment along with the air intake on the pump. The air intake on the pump is not as effective because if you want more or wetter skimmate then you increase the airflow into the pump, which in turn decreases the water flow . With this mod you can change the airflow independent of the water flow. Be careful though, you can crank it way up on the bubbles and it will overflow, it's not that bad it just drips some foam, but still keep and eye on it. I set mine where it takes about 2 minutes for the bubbles to reach the top of the inner tube on the collection cup.