A filter is a must have for a shrimp’s home. It helps control chemical levels in the water and generally filter out the bad stuff. When choosing a filter, I strongly suggest using a sponge filter and is the only type I would recommend. Dwarf shrimp are extremely small averaging just over 1 inch long and can easily be sucked up into a regular filter. You can make your own or buy one already made.
In regards to sponge filters, a double filter is best. The main reason for wanting a double sponge filter (a filter with 2 separate sponges) is to make cleaning the filter a whole lot easier and worry free. Good bacteria will build up on the sponge. By having 2 sponges, you can alternate the weeks it is cleaned there by always having one of the sponges left with the good bacteria still intact. And by cleaning, I only mean rinsing it out, not hosing it down and scrubbing it with soap.
*Tip: When cleaning the sponge, use water from your tank to rinse it out. Regular tap water contains chemicals that could throw off the balance of the water in your tank.
The filters listed below are the best ones I have come across. They are cheap, last a long time, and do a great job keeping a tank regulated. There are two sizes, small and large. The small size, which you can purchase from me, can handle up to a 10 gallon tank. The large filter can handle up to 30 gallons.