BigJim
Aquarium Advice Addict
I also run an AC70 on my 29g and I haven't replaced a thing. I used the carbon to remove tanins from a new piece of driftwood and threw the carbon out when I was done. I don't run it normally. As long as the BioMax is in nugget form, not powder, it's fine. I believe it's just specially shaped chunks of ceramic. Nothing to go bad there.