So I read that if I put things from tanks that have already been cycled and add it to my still cycling tank it will speed up the process. I found my filter from my old tank and was wondering if the bacteria could have died? Should I still add the filter? It's been in my laundry room for at least 3 years.
Seeding will only work if you're pulling seeded material from an active tank with an ammonia source (i.e. fish). If the seeded material has at all dried out then the beneficial bacteria is likely long gone.