So /an/, just built this.

Two lightbulbs, the lower one with aquarium gravel, the upper with all the guts of a filter. (Activated charcoal, that filtery flossy stuff)

An air pump runs through the smaller hose, pumping air into the bottom of the bigger hose, raising water into the filter lightbulb. This trickles down along the media and sides of the bulb to the opening, where surface tension causes it to run down along the same tube it came up.

Would it be okay to put like three tiny fish in there? Or would they fucking die?

I made this possibly overkill filtration system because I want to keep fish in a tiny tank that looks cool on my desk without having to replace the water every other day. Also it looks cool.