Worked instantly out of the box. Took a while to figure out how to set it up. The little green water force lever wasn't attached, was simple to put on again, also easy to access to the filter media for cleaning/replacement. The water force is very strong for a small tank, had the fish going in circles, was able to reduce it with the green lever and twisting the water direction dial, plus putting plants infront of it. It's okay now and how it should be, however I decided to also buy a power timer so the fish can get a break for 6 hours over night, just in case. The unit can make bubbles, but it's a bit unclear on how to optimise for this, the air tube needs to be outside the tank, it's quite short so you can't have the pump too deep without extending the tube. It has 4 suction cups that work well. I've found that the unit tends to make more bubbles when lying flat fully submerged rather than vertical. When vertical it will only make bubbles when the green water force lever is opened about half way and above, to get bubbles at lower pressures you've got to fiddle with it, turning the direction dial and adjusting/tilting/turning the unit until it starts bubbling again - not too tricky, takes a few seconds, but not entirely clear what the turning point is other than trial and error.
overall, works great, good 2 year warranty, does the job, tank is clear, fish are happy.