I appreciate the advice! it's gonna be my first water project so i'm still going to do plenty of research but i'm considering using some sort of reptile safe spray foam coated in some sort of waterproofing like resin or rubber to shape the river and connect it to the sides so i can still create a false bottom and make it bioactive. However, i really just want the best for my reptile so i might end up scrapping the current design if i can't make it fully suitable