Biorb help

[Zoeeannee]

I have just started setting up a biorb classic tank that I used to use but decommissioned. I have 3 other well running tanks but I have put my filter in and now can’t get the bottom bit of it out. I can’t take the top tube bit off but can’t get the bottom bit out can anyone advise?

 

[WhistlingBadger]

I'm not familiar with the biorb. Can you share a photo of the problem?