When we say cycling, we're referring to the Nitrogen Cycle. This is the process by which specialized beneficial bacteria colonizes the filter in your tank. This bacteria feeds on the ammonia that the fish constantly excretes through its gills, and turns it into nitrite. Ammonia and nitrite are both very toxic, and are dangerous to your fish at any readable level--this means that as long as the tank is not cycled, you must do frequent 100% water changes in order to get rid of ALL of these toxins. If you do one 50% change one day, and the next day do another 50% change, even though this adds up to 100%, there's inevitably toxins left over. However, another variety of bacteria eats nitrite and produces nitrate, which is much, much less toxic than ammonia or nitrite. Nitrate is only dangerous at high levels, so this means it's ok to maintain some nitrate in the tank, so you'll only have to do a partial water change instead of frequent 100% changes. Sounds a lot better, right?
In an uncycled 5 gallon tank, you should do 1 50% change and 1 100% change per week. When you do a 100% change, everything should be totally cleaned out with hot water to make sure you didn't miss any poop/uneaten food/debris. In a tank that is less than a gallon, you should be doing daily 100% water changes. If you cycle this 5 gallon, you should only have to do one 50%-30% water change per week, depending upon your feeding habits and whether or not you have live plants (they help a lot because they eat ammonia/nitrite/nitrate).
The nitrogen cycle is not something that just happens, it's something that you have to go through with a certain degree of intent. You need to have a freshwater master test kit so you can monitor the levels of ammonia, nitrite, and nitrate throughout the process no matter which method you choose. I highly recommend researching and conducting your cycle using the fishless method. A simple google search should tell you just about everything you need to know, but if you're still confused, I can explain that also. Using this method you will not risk harming your fish, you will get a more stable bacteria colony, and it's a lot less of a pain in the ass, in my opinion, than putting your fish in and constantly worrying about keeping the ammonia just high enough to feed the bacteria, but low enough to not harm the fish--just a lot of needless effort for a little instant gratification.
You may want to go get a larger container for your fish to live in while you're doing your fishless cycle. I recommend getting a plastic rubbermaid/sterilite storage bin from walmart or target. 4 gallon bins are only about $3 and are safe to use with a heater (which you will need, I recommend a 25 watt heater with an adjustable dial, the other cheap ones aren't worth your money). These bins are also durable and have a very ideal shape since bettas enjoy wider, more shallow tanks. You also won't have to change the water in it as much.
Last edited by Adastra; 07-19-2010 at 12:25 AM.