I've cycled 13 tanks with either Bio Spira alone, or Bio Spira in conjunction with other media.
I have a 90% success rate of a 24 hour cycle. The largest tank I cycled in 24 hours was a 75g and I used Bio Spira and the Magnum HOT off my 36g. Call it cheating a bit, but it was a bit of an experiment. I think of it as adding two packages of 90g Bio Spira at once.
One 65g tank took 3 days with no filter media. One 36g tank took two weeks and it was my OWN darn fault. One 75g tank took 1 week and that was with several seedings of filter material.
Still, even 1 week is far better and easier on the fish than 4-6 weeks without Bio Spira.
All the rest of the tanks cycled in 24 hours with no addtional help.
If you decide to try it, follow the directions on the Bio Spira package EXACTLY. SHAKE THE HECK OUTTA THE BAG
Do not put anything in your tank other than Prime or Marineland's Bio Safe to condition the water.
Do not change the water for at least 48 hours.
Add your fish at the same time as the Bio Spira, you don't add it and then add your fish later.
Roan