Good afternoon. I want to inform you that I had an emergency, I waited too long to go to the store to replace the Top Fin filters. My fish could die and I could have an electrical overflow problem in my tank. I used Top Fin to replace the filter in my 29 gallon tank. They worked great in our 29 gallon tank. Everything was just like it was written in top fin reviews. And given that the top fin filters are pre-assembled and have two carbon chambers, they are less messy and work better.