Yes this has been done. Just stuff the filter with filter floss, hang the return in the tank and use the intake to suck things up. I've seen it done on youtube to trim moss (because the moss sinks instead of floats like other plants.I have an old fluval 204 that I’m thinking of using to do tank cleaning(gravel), would that work? I have a 16gallon tank and would like to have time to clean before I siphon to much water out of the tank.
Thanks