Weird Fermenting activity - am I ok?

Hey all, first post here... glad to be among some experts while enjoying my new hobby!

I am in the fermentation stage of my 2nd batch of beer and the fermentation is acting completely different from the first, and also different from everything that I've read. I bought a Porter kit (brewer's best, I think) and followed the directions all well except that I had to boil a little less water than it called for. Instructions said 2gal. but with my smaller pot, could only fit 1.5 with 2 cans of extract. Anywho, everything went as planned, racked the beer in the fermenter at about 11pm and at 6:30am the next morning, it was already giving off a lot of gas bubbles, and much more rapidly than my first batch. Figured it was because I pitched it a little better this time and aerated the beer better before pitching (after it was already at 70deg.). But later that evening (14-16hrs later) The gasses had stopped. My first batch didn't start fermenting for at least 24hrs and stopped almost 2 days later. Should I be worried?

Oh, and one more thing I did differently was that I tried to fill the fermenter up with CO2 before sealing it. Somebody had suggested this to me to help minimize the oxygen content. Not sure if this was a good idea or not figuring that the yeast needs oxygen as it's fuel right?

Sorry for the novel, just a little concerned.

Cheers!

How did you fill it up with co2? Your beer needs oxygen first to ferment. No need to fill anything with co2 until you keg. Sounds like you are fine. Your ferment was hard and fast(keep mind out of gutter!) But stay away from putting co2 in your ferment.

loop

I have a plastic bucket fermenter with a small hole in the top for the fermentation lock. Before putting the lock in, and sealing the top down, i pumped some co2 in from the line through the hole in the top. I guess since co2 is heavier, it will force the oxygen out the top of the lid around the edges. I thought the oxygen in the wort was enough for fermenting, am I not right?

EDIT: Nothing to worry about with the really quick, and aggressive fermentation?

Thanks!

Really quick and aggressive fermentations are often sought and often achieved by using a starter or leftover trub from a previous batch. You can even do a search and see how people "aerate" their wort with pure oxygen while fermenting. So stay away from adding and co2 on your future batches while they are in your primary fermentor. It is after the primary that you want to avoid oxygen contacting your beer. And I'm sure your current batch is fine so relax, don't worry, and have a homebrew.

cheers,
loop

Well, since hydrometers are evil, there's no way for you to know if it is done. I've had over-night ferments. Wait the standard week.

The only time you want oxygen in your process is at the beginning of the ferment, more is better.