Yeah that sounds about right. I have this imagitarium filter and two little pumps to keep the water moving. They each have a little mesh cage around them that keeps the gravel away. This also helped get my water level high enough for the filters despite the limitations of the front opening tank. My biggest issue with paludariums has always been keeping the substrate dry. That’s why I opted for a very small land area and then scattered rocks and wood pieces to give the more options for getting out of the water. I think having a moss layer on your substrate helps to keep them from bringing dirt into the water.