How can I open this?

[Miami Reef]

Bulk reef supply had a video of someone simply unscrewing this pump easily. I am trying with all my power and I can’t get it open. I even tried tapping it to the floor to see if I can get it unstuck.

How can I open this before I break it trying to figure it out myself? Why do I want to open it? Because it got sand inside and the pump speed is slower.

 

[Miami Reef]

The part my thumb is on is the part that needs to turn.

 

[DrZoidburg]

Its abs plastic so it would contract in cold. Putting pump in a bucket of ice water might help. If it is precipitation soak in an acid.

 

[rusty hannon]

it almost looks like its opened a wee bit, and if brs shows it easily coming apart then i believe your sand problem is the problem(da) I would get a 5 gal bucket, fill 1/2 w water and agitate lots and see if u get movement. Repeat as needed.(probably many times)