Originally Posted by
Jandiscus
My reasoning would be the following:
1. Has the filter medium been used in one of your previous tanks or is it coming from somewhere else? If it is yours, maybe.
2. Did the previous tank inhabitants exhibit any health issues? If yes, I would start from scratch. If no, I would lean towards using it and have a fully cycled tank from day 1.
3. If it came from a clean and healthy tank of yours, I would carefully rinse it to remove solids without killing the bacteria.
4. Run it in your new, clean tank and feed it with ammonia for a while as an extra precaution. This might help in reducing/eliminating any remaining pathogens in the absence of hosts (fish).
5. If no risk is too small to avoid, start with a fresh setup and cycle until NH3, NO2 are zero (45 days or so in my experience when keeping NH3 at 2mg/L)
Others might have different and better ideas.
Cheers,
Jan