3 Gallon Shrimp and Crab Tank

I recently sold my 20 gallon tank and gave my corals, sand, rock etc to some relatives.

Already I'm going into withdrawals!  I'd like to do an easy micro.  Something I could move to another spot in the house if need be.  Here is my plan:

Marineland Eclipse System 3(three Gallon) using the included filter and lighting for now.
Hydor 2 to 5 gallon Heater
I can easily get some of my LR and sand back from my relatives.

I'd top off the evaporation with kalkwasser(pickling lime) and every week or two do a quart water change.

The plan is to have this be shrimp and crab tank.  Maybe a cleaner shrimp and arrow crab and of course a few cleaning crew members.  I may do one royal gramma as an only fish, I'll see how it goes.

In the future I was thinking of adding a Rio mini sun led  light to the setup.  Anyone have any experiance with these?

Am I nuts?  Any input or suggestions are appreciated.

if you step it up to the 5 gallon you will be doing a lot better. plus a bit more volume. you should get a powerhead as well. atleast if you go with the 5 gallon, the custom fitted filter hits 65 gph so it depends on what you want to get gph wise