I once made a refugium from an Aquaclear filter, and one of the things I read was that you should remove the impeller and replace it with an impeller from a smaller model of Aquaclear, to slow the flow. I assume you will be using chaeto in there eventually- the slower flow maximizes the water's contact time with the chaeto and is theoretically supposed to be better at removing excess nutrients. With the comparatively small media compartment on the Top Fin filter, and the higher flow rate, I'm not sure it's really going to do much as a refugium. On the other hand, extra biomedia and additional flow won't be a bad thing, I'm sure, even if it doesn't really function as a fuge.
It's good to hear that the scooter you bought will actually accept prepared foods. Many won't and are starving half to death by the time they are sold. One of the most important things to do IMO when you are purchasing any new marine fish, is to see it eat. Don't be shy about asking them to feed the fish while you watch. LFSs get that question all the time. If you don't see the fish eat, don't buy it.
