Betta fish swimming on one side of tank

Question
QUESTION: Hi there! I purchased my betta fish (buddy) a week ago and he is a really
hard fish to read, he is blowing alot of ubbles around his entire tank and
he is swimming alot with his fins out, when we first got him I pit him next
to a jar that bad my sisters betta fish he flared and did all that good stuff
and seemed really happy about defending his territory, I got hima bigger
tank and the first day he was excited, he explored all over the ace and
everything was fine, right now he seems to only like one area of his tank,
he will swim around the part with leaves and he will occasionally go to the
other side that has a shipwreck marbles and gravol, his other side has
live plants and gravol, I also put a mirror infront of him one day and he
didn't flare, instead he ran off and hid in his ship wreck, is that normal??

ANSWER: Anthony,

Where bubble nest building can be a good sign of a happy healthy fish, it can also be a bad sign.  You didn't mention a heater. He needs one. Water has to be 82 degrees no less. How big is his tank? Do you check his water for ammonia, nitrates, nitrites and ph? Do you do water changes and add a water conditioner to the new water being put in his tank? When you do the water change is the temp of the new water the same temp as the water still in his tank? As soon as you answer these questions, I can start to figure out what is wrong with your Betta.

---------- FOLLOW-UP ----------

QUESTION: I do not have a heater and I never checked for those nitrate and ph levels,
he is in a 4 gallon tank and when I change the water I add in some
amounts of chlorine and I let the water sit for a day, then I gradually add
him into the water so he gets used to the water, I tried to show him his
reflection again and this time he flared and expanded his gills, however he
still will only go to the other side of his tank on occasion, in his old tank
which was much smaller he used to swim all over the place, I hope this
information can help you! Thanks again
Anthony

Answer
Anthony,

When you change his water, you want to remove chlorine not add it in. That is most likely the problem. I would do a full water change on his and add a conditioner that removes chlorine, nitrates, nitrites and other harmful things from the water. Never add chlorine to his tank. You do not need to get  him used to his water. As long and the water being added is the same temp as the water he is in already, you can just place him in his tank immediately after the conditioned water change. Once you remove the chlorine, I think you will see a huge difference in him. If you don't want to add a conditioner that removes chlorine, let the water sit for 24 hours before you put it in his tank. During that 24 hours the chlorine will dissipate and will not be there when added to his tank. But it is a good idea to get a water testing kit, water conditioner, and a heater if you want your Betta to be healthy, happy and around while.