It’s an Oase Biomaster thermo 350. My boyfriend has used a LOT of filters over the years and he really rates this one (mainly because there’s a pre filter so you can clean it without having to take whole thing apart).

And it has a heater in it, so that’s one less thing in the tank.

The one complaint he has is that the flow control is on the outlet and inlet pipe work that’s in the tank, so if you don’t have that fitted you can’t adjust the flow rate.