Hey. so i just got two new 5 gallon tanks for my male bettas. how to i cycle them?

[Alicia]

But the filter media has not been used for way more than a couple weeks. 

[Schwack]

If I had to guess, you've got some filter carts with a bunch of dead bacteria on 'em. Are the fish currently in smaller containers without filtration or an established cycle?

If that's the case, I'd get them into the 5 gallon tanks ASAP. An uncycled 5 gallon at least gives some water volume for you to work with while cycling. I would discard the old filters and carts and just use sponges. Give the filter media a decent rinse as well, introducing lots of dead bacteria into your new tanks is a good way to get an immediate ammonia spike. You're basically starting from scratch with a fish-in cycle, but bettas are tough and will typically come through without issue. 

Keep your eyes on ammonia/nitrite levels and water change as neeeded. Something like 30%-50% when you see ammonia hit .5 ppm or nitrites at .25 ppm. You can probably go higher on those numbers, but 5 gallons are easy to water change.

[Alicia]

Ok will do. What about the gravel and decor? It’s probably dead bacteria  too? So just give the decor a rinse and start again? When I first got my betta it was defiantly a impulse buy and so the tanks where bit cycled . Just a HOB filter with decor and pebbles. Will the  live bacteria I got help?  

[Alicia]

Also what is some black gravel you can recommend ? 

[Schwack]

Have the fish been in with the gravel/decorations/etc? If the fish have been living, and pooping, with that stuff, it's almost certainly got live bacteria on it. If it's been in water with no fish for more than a week or so, I'd give it a bit of a rinse and put it in the new tank when you add the fish.

Some people swear by bottled bacteria, but my experience with multiple brands has not been positive. If you've already bought it, I'd definitely add it, but don't expect the tank to be cycled in a day. It's likely going to be a few weeks before you can dial the water changes back to once every few weeks or so.

[Alicia]

Ok thank you, yea I already bought the bottled bacteria. Can you tell me the steps of what I should do for setting up this fish in cycle? 

[Schwack]

https://fishlab.com/fish-in-cycle/

That's a pretty good resource for a fish-in cycle. 

From my understanding of your situation, I'd want to get your fish into the larger volume containers as soon as possible. Clean up the gravel, if it's been without fish/fish waste for a week or so, and get everything rolling in your new 5 gallons. The added water volume gives you a lot more room to maneuver in terms of increasing ammonia/nitrite.