The only issue with mine is that I battle to open it! It's like it sucks tight and you need some seriously strong hands to get it open... I'm in that situation again now... it needs a re-wick... but I can't get it open... So it's laying at home patiently waiting for strong hands to help me out... The wasp nano is in use again now... at least I can open that one by myself!!
Hi @Tanja
My mom used to have the exact same problem with the old Nautilus Mini. She couldn't open it after a while. Not sure exactly why that happened but I think the suction contributes to it. The solution was to put some VG/PG on a finger and lubricate the rubber o ring that the glass made contact with - every time she opened it. That sorted it out.
The other way is to try open it with rubber gloves that give you better grip.
Not sure if this will help you with your tank but worth a try