So guys what do i need to do? i most probably wont change the tank. Just want to know how much should i wc per 2 weeks? or refill the water from a pail is good enough?
You need to take the advice these nice people have given you, because the way you're thinking right now will not end well for you or the fish.
1. Change AT LEAST 40% of the tank water weekly.
2. Use a good dechlorinator. If you are changing water with a bucket, add the dechlorinator to the bucket before pouring it into the tank.
3. Make sure the water in the bucket is a similar temperature to the water in the tank.
4. Plan to upgrade your tank ASAP, the aro will out grow the tank you have now.
5. Listen to any other advice given to you by these guys, they are very smart people with a lot of years of experience between them.
I've written this as simply as I can, and if you do these 5 simple things and you will keep your fish happy and healthy for years to come.