Okay, so I had originally intended to house a betta in this tank, but it has become a shrimp-only tank. While preparing to house the betta, I did two things to reduce the flow of the pump.
My first mod to the pump was described on page 2 - I cut a small hole in the outflow line so the water level in my pump chamber would rise and circulate since there's a heater in there.
The second was to put a Fluval Edge prefilter sponge over the outflow nozzle.
Now that I've decided on shrimp only, I don't even need the heater, and will probably remove it at some point, although I haven't yet.
I explained all of that to ask this question:
The filter sponge I put on the outflow is apparently full of mulm that made it through the crummy mechanical filtration of this tank. My shrimp are constantly feeding on it, and so are my pond snails. I can even hold a shrimp net in front of it and poke it with my finger to dislodge a whole bunch of nematodes, catch them, and feed them to the betta in the other room.
If I remove the filter sponge, I have nice flow in the tank and lots of surface movement. Currently, there is none and my floaters, although gathered at the filter overflow, seem to enjoy the lack of current. If I remove the sponge, will the shrimp care about the increased flow? Will the little random floaters (not even sure what species they are) care about having flow and movement on top of the tank? I am not injecting anything except liquid ferts, this is a very low-tech setup.