With great excitement I ordered the Hydra Aquatics Nano Vortex Flow Spinner to put in the Fluval Sea 5. No luck - it is a screw in and there aren't adapters to make it work.
I decided to try it in my Fluval Sea XII. It fits. But does it spin?? NO. Not a millimeter.
I have the Hydor spinner thing and it sticks out of the water and spins like a champ. This thing sticks out of the water just a bit and doesn't spin a bit.
So, I'm not griping I just wanted to save others who own the aforementioned tanks time and money by posting this here as a searchable thread.
Marine Depot was great and refunded my money and told me to toss it.