The fan has been bought and is now in the tank. Still need to figure out the modifications to make to make it critter safe...but I think screening and silicone/gorilla glue oughtta do it.
Latest photo of the tank. On the right is a water feature in the making.
Do you think this would work for little epiphytic orchids? A bit of sodium bentonite clay was first mixed with Home Depot Aquatic plant soil(basically pieces of clay gravel) and smeared onto the branch. After that roots from other plants, leaf litter, moss, etc. were clumped ontop of it. Here you can see a microgramma fern cutting set to go on this branch. I'm not sure if they will dry out but so far so good.