I keep a Penn Plax Sand Shark Internal Filter in one of my tanks to use when I need to set up a 10 gallon as a hospital/quarantine/larger fry tank. Instant cycled filter! It's also nice to have the dual filtration in case one of the filters goes out. It says it is for terrariums, but that basically just means it is fully submersible.
Today I discovered I could pull the top off of the replacement carbon cartridge (which I always like to do because I don't bother with carbon) and that 5 ceramic rings (which I use with my Filstar cannisters on other tanks) fit neatly inside it. So, now my little Shark is a biological/mechanical filter, I can squeeze out the sponges with impunity. Neat.
Today I discovered I could pull the top off of the replacement carbon cartridge (which I always like to do because I don't bother with carbon) and that 5 ceramic rings (which I use with my Filstar cannisters on other tanks) fit neatly inside it. So, now my little Shark is a biological/mechanical filter, I can squeeze out the sponges with impunity. Neat.
