Well you can't cram too many shrimp in there anyway so you won't need a massive filter, and you will still need to do water changes. A filter simply means that if you do have to miss water change or two for some reason (illness or whatever) then the tanks inhabitants are far less likely to suffer from the effects of their own wastes, because the bacteria in th filter will process them and break them down. In a non filtered tank the wastes would simply build up and eventully poison whatever lives in there.
Filters do a lot of work for you in simple terms.
But shrimp do not produce much waste, and as long as you don't overfeed them, a little filter like that should tick over just fine and you'd really only need to do a 25% water change every week for a moderately stocked tank containing around 5 shrimp.
Having live plants like the Java moss and mossballs will also help keep down any nitrates, and shrimp realy love to pick bits of food and biofilm from moss and suchlike.
You don't even really need a substrate at all for that tank if you have moss. You could create a moss mat for the floor of the tank, a living substrate if you like.
Just cut two pieces of plastic embroidery mesh to fit the inside dimensions of the tank (make sure the holes aren't too small ) , cut out a corner for your filter to sit in, and between the two sheets of mesh, spread an even layer of Java moss. "sew" the edges of the mesh together carefully to trap the moss inside and place it in your filled tank under the light to grow through the gaps in the mesh . It may take a while but you should get a good decent carpet of moss for the shrimp to live in.
Basically it's the same method as creating a moss wall which most people have on the back wall of a tank ( attatched with suction cups ) but instead it's on the base of the tank.
You could even have a go at doing 3 walls and a floor all in moss using that method. That would look pretty unusual..
good to know.
