I've always just done water changes instead of cycling(as most of the time my fish are in smaller tanks) but since my 20long is empty for a while i'm thinking of cycling it.
I don't want to do a fish-in cycle and risk the health of the fish, and I know I can add pure ammonia(if I can find it).
But can I add water from my water changes(poop/uneaten food) instead? So that it's essentially a fish-in without the fish?
Also, would adding 'gravel' and decoration /after/ it's cycled effect it/make it start over?
And, most filter cartridges have charcoal in them. I have a few old cartridges without the charcoal. I'm assuming the bacteria just need a place to grow, so instead of adding more coal can I leave them empty or fill them with say tank gravel or bundled up cheese cloth?
On a semi-related note, had anyone here used the Seachem alert devices for ammonia/PH? Are they reliable/accurate?