I have the penguin 350 running on my 90 gallon tank. My question is, where is the actual filter material located? I take the top off and I see two slots at the back behind the biowheels. But these slots just appeared to be filled with rocks from what I can see. It doesn't look like carbon or filter material. Maybe I am nubs but any help would be appreciated.
Thanks,
Logy
Thanks,
Logy