ill betta

Question
my betta jaws is lying at the bottom of the tank, whats wrong with him?

the tank doesnt have a filter as i have to use it in my 20 gallon until i can get a new filter. the tank is 10 gallons and he shares it with 2 other bettas (all sectioned off from each other). well this betta (jaws) hardly moves anymore. i mean he used to swim all over his part of the tank, now he hardly does. the tank is heated and he does have a great appetite. i mean if i hold a small bit of prawn in the water he will go crazy and thrash his head from side to side to rip and bit off and he will eat it.

i change about 50% of the water once a fortnight or 25% once a week.  

Answer
Sarah,

Sometimes our fish do things that we don't know why they do it. I had one the other day doing the same thing but now he is fine. Make sure you are testing the water every 5 days or so to make sure the ammonia nitrate and nitrites are all correct. As long as he is eating and not showing outward signs of illness, there is no need to medicate him with anything. I would just keep an eye on him and make sure he looks ok. If things change for the worse or he isn't acting better in about 5 days let me know.