Tub Filters: Filters used for turtle tubs must be carefully thought out. Hang on the back filters most likely will not work. That leaves internal and canister filters. Internal filters are great if you can afford the space hogger. Otherwise, canister filters are excellent options for large volume tanks. However, you do need to keep one thing in mind if you are planning to use a canister filter. A majority of turtle tubs will be on the ground or floor. Many canister filters work properly when underneath a tank. Some even require it. There are some exceptions and in some cases its just a small decrease in performance. It is recommended that you elevate your turtle tub, if possible, at least a few inches to help the filter out a bit. For example you could use one or two layers of cinderblocks with a plywood piece between the top layer and the tub. The LLYT turtle tub is currently on one layer of cinderblocks. The setup has a Fluval FX6 running next to it. There was no noticeable decrease in performance.