Hi! I have a 30 gallon with a Penguin Biowheel 70 HOB filter that I wanted to get rid of hopefully because they make noise and drive my husband crazy, especially if I am not here to troubleshoot. So I added a double sponge filter about 2 weeks ago. Yesterday, I added an Aquaclear 30 Powerhead with quick filter. It looked fine until we went to bed. When we got up this morning, it looks like it is either producing a lot of micro bubbles or blowing sand (I have a sand substrate). This tank is cycled and has 12 inhabitants. Fish are fine. I am just concerned if it's blowing sand that might be a problem.