Anyone have any idea what's on the bottom of my heater? Thought it was air bubbles but on closer inspection, I see it's something else. This is a new heater and was put in just a few days ago. Deffinatly didn't come that way. Anyone seen this before. They are SUPER small but they are not flat, that's for sure. Have 9 tetras (5 glow, 4 whites), 3 ghost shrimp and two tiger nerites in the tank.