14g biocube spewing bubbles after alterations

So I have a 14g biocube and I made some alterations based on suggestions. I have the original carbon filter pad that came with it installed in the third chamber, i removed the bio balls from the second chamber and put some live rock rubble in there, and I removed the sponge from chamber 1. Before removing the bio balls and the sponge i had no bubbles spewing, but afterwards they are coming out pretty good into the display area. I've checked to make sure that the pump is secure and the hose is connected so there shouldn't be any air coming through. Again, this only happened after removing those two things. I've attached a photo for what I have now ( I threw the sponge on top of the live rock in the photo to see if that would help and it didn't but I didn't remove it before taking the photo so just ignore it ).