Red Sea nano tank

[Shanephillips27]

Hello all. I’m hoping some of you can help me solve this mystery. I have a red sea nano max peninsula 26 g aio and I’ve noticed that in the rear chamber where you put your filter sock or filter floss. When mine is ready to be changed I place my hand in there and pull the filter floss out but upon doing so and after I’ve replaced with clean material it raises the water level about 1.5 to 2 inches for a few days till it decides to settle out and go back down. Any idea what this might be or what’s causing it to do this every time I change filter floss? TIA

 

[Flameback Pair]

It’s purging the air out of the filter floss.

 

[Solo McReefer]

Air