I can't believe no one answered this but it may have got lost in the shuffle. If you haven't got it already, get a siphon / vacuum like: http://www.petsmart.com/product/inde...ductId=2752298
They come in different sizes depending on the tank size. Once you get it started, just hover the vacuum end about an inch over the gravel (or whatever distance doesn't suck the gravel up) and sweep it across all the substrate. Good luck!
Proper gravel cleaning-(without live rooted plants).....the vacuum needs to be plunged into the gravel to the floor of the tank and as the water clears move to different areas to clean/vacuum the gravel in all areas that can be reached without moving anything in the tank (like the decorations) the gravel should slightly move up into the vacuum and turn over as it removes the mulm/debris...
This will help to keep anaerobic areas from forming, allow oxygen to the sticky beneficial bacteria that has colonized in the substrate, proper removal of mulm/debris/waste that has gathered...among other things......*this is especially important if you have UGF to keep the plate clean and working properly....
With live rooted plants you don't want to disrupt plant roots- hovering over the substrate lightly is all that is needed....
In the smaller tanks-often the stir and dip method is more effective......use an item like a chopstick or wooden spoon to give the substrate a slight stir and dip the dirty water out
Remember to wash your hand before and after cleaning
Unplug both the filter and heater before starting to allow the heater to cool slightly-this is if the water level is dropped lower than the heater so it doesn't crack/break
If its time to clean the filter media(a couple of times a month)-give it a swish/rinse in the old tank water to remove the big pieces of gunk (you want the filter media to look dirty-this is the good bacteria)
Re-fill with like temp dechlorinated water using dechlorinater for the volume of the tank not just the volume you are replacing-make sure you are using enough dechlorinator for both chlorine and chloramine-(some dechlorinator require double with chloramines-check your label)
Once the filter has been re-started the water should clear within an hour or less if you have been making regular water changes and not overfeeding.
Watch out that you don't suck your betta up in the syphon! I was in a hurry once & did that - didn't realize it & down the toilet he went!!! :( Didn't even notice till later in the day. I felt just AWFUL!!!!
I take my betta that I have in a 2.5 aquarium out when I siphon his since it's a much smaller area, and I have a big gravel siphon. When I siphon my 48 gallon I don't remove my betta since he will stay at the top (nipping my fingers as I clean the tank on his side lol)