Prior to their arrival, I had set up three separate tanks. However; since they are small--I decided to keep them together until they grow some. It looks like they could very easily be sucked up a filter intake.
Right now it is a bare bottom 20 gallon hex with a Tetra Wonder Water filter. The filter is totally enclosed inside the decorative "rock wall ornament" in the photos. I felt that was the safest option other than a sponge filter for now.
Yah, its so ugly its kind of cute. Pre-historic looking with those external gills. I like one of the descriptions I read - they are an example of de-evolution.