Changing The Water
With normal tank water conditions you should consider changing the water at least once a week or at an absolute maximum of every two weeks.
You shouldn’t change all of the water at once because this may cause your Bettas to stress-out, and will more than likely cause your Betta more harm than good. You should replace about 10 percent of the water each week or about 15 to 20 percent every two weeks.
Keep in mind that smaller amounts of fresh water changed often is much better than larger amounts of water that’s changed less often. Remember that larger amounts of fresh water can change the water chemistry, resulting in extra stress being placed on your pet Betta.
Changing the water in your tank
Firstly, vacuum the gravel to remove all types of leftover food particles which is probably decaying and causing pollutants like phosphates, and harmful ammonia. Remove all decoration rock, and vacuum underneath them as well. Be extra careful as not to suck-up your fish hiding in these areas.
If you have put a filter under the gravel, then you should always vacuum more often to stop the formation of harmful nitrates. In addition, you should scrape off any excessive algae you see on the glass, and also from assorted tank decorations.
It’s vital that you thoroughly wash-out the aquarium tank using a clean, non-abrasive sponge and/or a soap-free brush.
Make sure it’s kept specially for the purpose of cleaning your tank ONLY! Keep in mind just how much water you wish to change during the cleaning process, and measure out the required amount of water conditioner exactly. You should always keep water conditioner close by and handy.
Also, make sure that you unplug the heater, filter system and tank lights. Then as you siphon the tank water, and store it in a measuring bucket or clean container. After you’ve siphoned the water off, go about replacing it along with the rocks and tank decorations which you removed during the cleaning period.