No one said there wasn't bacteria in the water. It is minimal at best. If you want to seed a new tank, you need to use gravel, decorations or filter media from an established tank (best option). If you use just the water from the old tank in the new tank, that bacteria will die off before it starts to grow. You will basically be starting from scratch.
1 Gallon Bowl - White/Purple Half Moon Betta
1.5 Gallon - Blue Veil Tail Betta
2.5 Gallon - Red/Blue Veil Tail Betta
2.5 Gallon - Pea Puffer
5.5 Gallon - RCS, Ghost Shrimp, Ember Tetras, Sparkling Gouramis, Bumble Bee Gobies
10 Gallon - Pure Black Bar Endlers
29 Gallon - Planted Community - Cherry Barbs, Neon Tetras, Various Cory Cats, Albino Bristlenose Pleco