I am leaving my residence for 6 weeks in the summer and I decided to redesign my filter based on a YouTube video I saw so that I don't have to swap out topfin cartridges. I'm not the biggest fan of them and I avoided changing them anyways. But the water was rising and almost overflowing from the filter even after swishing them around in old aquarium water. The filter now has a Fluval sponge on the bottom of the hob, a topfin sponge on the intake, bioballs from Fluval and some old media on top. I left the bioplate with the original so I didn't deplete the bb during the change. After checking levels daily and adding a few dosis of stability, it has been perfect.