Do you need to have a canister filter in order to run a pressurized co2, or can you do it with a HOB?

You can do it with a HOB. But you won't be able to run a reactor.

and what does the reactor do?

Dissolves the CO2 into the water

So with an HOB i wont be able to dissolve the bubbles?? so how can you dissolves the bubbles with an HOB?

You can use a diffuser (limewood, glass, etc.), which will create smaller bubbles. You can position the diffuser so that the outflow of the filter pushes the bubbles around the tank, which will give them more time to dissolve. Or you could position it so that the bubbles are sucked into the intake of the filter and dissolved by the filter itself.

cool.. thank you very much for your quick replies.

No problem. Good luck!