So I bought this used for my brother's tank. The pump turns on but the bubbles are only about half way up as seen in pics. The unit was used so I'm not sure how to increase the bubble height so they will overflow into collection cup. I'm not sure if the pump is adjustable or maybe its wearing out? Or the air line is messed up? When moving the red air adjustable tube it just kicks back to where it was. Any insight would be appreciated!







