Hydor Koralia Nano Aquarium Circulation Pump, 425 GPH

I don't know how I figured 240 gph would be OK in my 20g long, but I did. I had to move it from where I had wanted it as it was so powerful it was sucking in all the bubbles from an air stone 8 inches away. First day I had it on, my fish went nuts in a good way. My corys were scuttling and drifting along their sandbed, my danios were chasing each other through the current, and my littlest tetras took turns darting directly into the jet only to be blasted into the opposing tank wall. I turn it on intermittently, and I can't leave it unattended in good conscience for my tetras sake, but I have it positioned on the back wall next to the outflow of my filter and pointed up at the water surface, and it makes my tank water go in circles. It doesn't stay put at the edges of how far it can be adjusted, but I've had more issues getting the suction cup magnets to detach when I need to move/clean it. I want to buy a powerhead better suited to my tank size but this one is so quiet and Koralia doesn't make anything smaller, so I'm happily resigned with blasting my tetras around now and again.