I have my betta fish in a 6.7L tank. Is this is a good size?

No, it's not big enough. He may be a small fish that is able to breath air, but keeping the water quality stable in a tank that size will be nearly impossible. For a betta, I would recommend the following:

A 5 (UK) gallon tank (about 6 US gallons)
A 25 watt heater
A sponge air powered filter
A few plants and some gravel.

He will not grow to the size of the tank, nor will any fish. This is a myth. If fish grew to the size of the tank, I would have myself a pet great white shark by now lol.

Make sure to cycle any new tank *before* you put the fish in, using fish to cycle is cruel and unnecessary.

Small tanks will cause problems firstly with water quality (ammonia burn, nitrite poisoning) then will come the secondary diseases (finrot, ich, bacterial infections, protozoan parasites) so it is worth starting out with the right equipment to prevent problems in the long run.

A lot of pet stores give spectacularly bad advice about bettas, so it's best to do your own research. Just because they can survive in small containers, doesn't mean they should be kept in them. In the wild, bettas can survive in puddles, but they actually live in streams and rice paddies, which are massive if you see a picture of one.

Here is some basic betta care info- http://www.thetropicaltank.co.uk/Fishindx/betta.htm

A couple of my friends breed these and they swear by 5 gallon tanks!

Comments

Thanks a ton for the info! I just wanted to let you know, though, that I change the water often, and I add AquaPlus water conditioner with every water change, and I add Cycle (a biological filtration chemical). Some bettas are kept in tiny bowls :o!
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by DarkFishy on August 25th, 2006
Yeah, that's cool, but what I'm saying is that if for any reason your filter broke or something, the ammonia level would become toxic a lot quicker in a smaller tank. You shouldn't need to add Cycle all the time if your tank has proper bio
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by gung-ho on August 25th, 2006
If you need to know anything else, feel free to email me. I am studying aquatics so I know what I'm doing lol.
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by gung-ho on August 25th, 2006
Yea! I love studying fish too. I really love betta fish, and i try to spoil mine, whos named Merlin. I know a lot about bettas, and i too try to help people with fish related questions (so leave some for me! lol).
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by DarkFishy on August 25th, 2006
Haha, sorry DF! I've got goldies in one tank and corys and peacock gobies in the other, have you got any others except your betta? Merlin is a wicked name.
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by gung-ho on August 25th, 2006
Yup, I've got four small goldfish in a ten gallon tank. I hope that soon I can put the goldfish somewhere else and put tropical fish in the tank. I'll try to put merlin in a 6 gallon tank when I've got the room. Thanks again for the tips!
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by DarkFishy on August 25th, 2006