I had a good experience with a filter with similar set up on a 100 gallon display tank with gravel and artificial plants containing angels and discus. We were expecting a big storm, so I quit feeding two days before. When power went out, I disconnected the filter and drained almost all of the water. I put the cover back loosely, so that some air could circulate, but not so much as to dry out the media. I did not feed the fish, and there was no heat and no artificial light, so everybody pretty much chilled out (temp was mid 70's). Water changes were not possible because there was no power for the well. I tested for ammonia each day, and none was ever detected. Bottom line, all fish survived just fine.
When power returned, I made a 75% WC and put the biofilter back into service. Fish were fed lightly for the next few days. No ammonia was detected, so the filter must have survived its ordeal. And so did I.