[MyraVan]

The bacteria grow on everyplace that it finds a good source of food, that is, ammonia & nitrite. More grows on the filter floss because there's a good flow of the chemicals that they eat going thought the filter. But even when you have a filter you'll have some on the gravel. So yes, adding gravel from your old tank can help jump-start your new tank.

But, this is important, you must feed the bacteria in their new home! If you don't, they will die. So pretty much immediately after putting the gravel in the new tank you must add a source of ammonia. That is, the betta, or else some ammonia to do a fishless cycle. And then the existing bacteria will live, and will propogate to get into your new bio-wheel.

So you can't use the gravel on its own to cycle the tank; it just makes either a fishless cycle or a cycle with fish much quicker, and much less hazardous to the fish if you go the fishy cycle route. Since you have a good colony of the bacteria are already there, much more of the toxic stuff will be broken down immediately rather than building up to really harmful levels before the bacteria grow enough.