Sick dieing? Betta

Question
i've had this Betta fer over a year now, but when i changed his tank two weeks ago, he started to float.  he us to be a bright red and teal colour, but now is a pale red almost white colour.  all he can do is float.  begining a couple of days ago, he started to grow a lump near in tail (tumor?)  his gills are black and are really sticking out far... is taht normal?  he hasn't been eating laterly and he just floats.  i keep him in a 1 gallon tank.  i change his tank once a week, full water.  i did a partial water change yesterday.  i don't know the pH or ammonia level and the temperature is a bit under the regular temperature they're suppose to be in.  my mom says he has a bladder desease, but it is taking to long to go away.  i don't know if he's sufferiong so can you please answer this question as soon as possible!!!

Answer
Hello Molly-

Be sure you're using water conditioner on the water. Untreated tap water can kill a betta in a few hours.  From the symptoms you've described, something is very wrong with your little guy. I recommend not changing his water anymore, but do add a dose of Melafix and aquarium salt. Try to get the water up to 80-83 F (you can use a desk lamp.)

I can't guarantee this will help, but it will definitely ease his suffering and reduce stress.

Hope this is useful,
Amber Worman