If your tank has been up for 6 weeks, it should be cycled. All tanks are different, though, and you should test to be sure your cycle is complete. Are the fish acting ok? Are they breathing from the surface (unless it's a betta or gourami) or lethargic?
Here's an article on cycling: http://www.aquariumadvice.com/articl...q=2&fldAuto=21
If you don't have nitrite or nitrate tests, take some tank water into your lfs
and they can test it for you. Ask them to give you the number result, not just tell you "it's fine".
It's usually best, IMO
, to let the cycle happen on its own, and not to use these bacterial additives to try to start it. The cycle does take a long time sometimes - 4-6 weeks or longer - but it's best for the stability of the tank in the long run to let the bacteria culture itself naturally.
I have used Bio-Spira, the live, refrigerated bacteria, and it did work well. It didn't cycle overnight but it helped. It's rather hard to get where I am. I am cycling my next tank with the fishless cycling method, where you add ammonia to the fishless tank to begin the cycle and let the bacteria colonize that way, without harming any fish.