After staring a the tank long enough I decided that I needed more greenery. The big plant (I have no idea what it was but the guppies thought it was delicious) came out, and was replaced by rocks and I went a little nuts with the planting. Since I'm not 100% on what I'm doing I took a scatter gun approach of sticking a load of stuff in there and seeing what sticks.
I still have the temporary lodgers who seem to have settled in nicely, and the shrimp are waiting to go back in, as I moved them to the 30 liter while I was planting, and I have found that they can get a bit stressed when I move things around.
I trimmed back the weeping moss from the cave as I needed some for the bowl Im putting together, and it seems to be growing really quickly in this tank so I figured it would regrow well enough.
Still need a background for it but I made the mistake of telling my wife she could pick one, which means that it may be well into next year before she finds one she is happy with.