HCA: Hermit Crab Association

In a 20 gallon you won't really have space to do filtered 2.5 gallon tanks within the main tank aned still have space for them to dig and molt. For my 20 gallon long I had deep tupperware containers with bubblers. I stacked each container inside another so that when I did water changes I wasn't dis...

Question: I have a 20-gallon tank and I'd like to set up a couple pools for fresh and salt water for them to wade in. I'd considered some tupperware with bubblers, doing water changes. Is filtration absolutely necessary? I have an aquarium so I understand how to set them up, the nitrate cycle and wh...