I have a divided 8 gallon tank which is filtered and heated with only a female and a male betta on each side. I have never checked the water values because my bettas are great. My question is:
How frequent water changes should I make and what percentage?
More info: It is not a planted tank. The temperature is constant 26 Celsius (80 Fahrenheit) in both chambers. The filter makes minimal water movement (the surface is perfectly still). It has been running for 6 days now and the water looks perfectly clear. I also added one small jar of water because of the evaporation.
Thanks! And the best thing about divided tanks is that I can clean one chamber at a time! My tank is divided with a plastic cover with 2,5x0,5cm horizontal holes all over but I also have a full glass divider which I will use when I clean the tank - it won't disturb the other chamber at all! :)
A tank that has only been running for 6 days needs to have about a 50% water change every 2-3 days to keep ammonia levels in check. I suggest getting a liquid water test kit so you know if your tank is cycling properly, otherwise you'll only be guessing when its complete.
I made the suggestion based on my personal experience with fish IN cycling, its up to you what you want to do. I tested my water daily & averaged a 50% (to keep ammo/nitrites at 0) water change every 2-3 days for 8 weeks on my 10g tank & my 46g took about 5 weeks to fish IN cycle. I always do a 50% water change as it doesn't hurt anything & I think, based on advice from more experienced aquarist, its better to give my fish as much fresh water as possible each week.
Once the tank is cycled, its the nitrates you need to keep in check with the weekly water changes as well as replenishing other minerals & such water contains. As I stated I always do a 50%+ water change on all 5 of my tanks, its up to you what % you want to do. Most experienced aquarist I've had contact with do 50%+.