I used biro spira on my ten gallon after only 3 days of having it up and running. I put my new pet crayfish in the tank at the same time. I was iffy about spira, but its been a month and my crayfish is alive and healthy, so I learned to trust the stuff. I'm setting up a new 5 gallon for a couple Corys , and I JUST set up the tank with the gravel, and filter. I added some water conditioner too. Do you think when I go to petsmart to buy the heater and thermometer, that I could buy some spira and the cory's also? Do you think it would be safe using spira and adding fish as early as a 45 minute aquarium?