bettas in plastic bowl

Question
I don't have experience with many bettas. I got my first one about a year ago. I've kept him in a glass bowl. He was always very active.
Then i got three crown-tail bettas, two of which i kept in glass, and one in a plastic container made for bettas hanging on the wall. The betta in this plastic container was never lively, and after a few months, was only swimming on his side (through both fins worked). So i ended up having to euthanise him. Then i put one of the other crow-tails, a very spunky one, in there, and after only 2 days he was sooo lethargic. I put him back in his glass bowl but he was dead the next morning. A few weeks later, my other crown-tail died in his glass jar. I thought maybe crown-tails are just weaker than regular bettas.
I decided to try my first betta in this plastic container. After a few hours i noticed he had a very hard time swimming down. So i put him back in his glass bowl, and by the next day he was fine.
A month later i decided to try again. He's was ok, but lately has been getting more and more lethargic. He just lays at the bottom, usually on his side, or with his head in a crack between rocks. Also, he's red in colour, but his head and belly are losing colour. He's still been eating, but comes to top now only to breath. He didn't eat yesterday, so i put him back in his glass bowl.
My sister also has one of these plastic betta tanks, and her betta hasn't eaten since she's got it, over a month ago. (Her tap water is very hard)
I do water changes twice a week, with tap (city, low pH) water, added with 'tap water conditioner'. The room temperature is quite consistent. And i feed him 2 dried blood worms a day.
I asked the pet shop if they've heard from anybody else about these containers. But they said anything made for fish is usually very well tested, and that my bettas might've just all died from old age, since they don't know how old they are when they receive them.
I've read something about aquarium salt, so i'll add some when i get home. But i'm not sure how much.
Do you know what might be wrong? Have you heard anything about plastic?
Please help me save my poor last betta...

Answer
Hello Joleen -

I am going to try my best to be polite as possible when I answer your question. Please understand that as someone who has kept and raised bettas for many years, it is very hard for me when I see bettas that are kept in conditions such as yours. I am sure you love your fish, and I am not trying to personally "attack" you, but bettas cannot live full happy lives in the environments you are trying to keep them in (as you yourself have experienced.) Much of this comes from lack of knowledge on the part of pet store employees. Very few know anything when it comes to keeping fish. (They're the ones keeping the fish in cups in the first place!)

First thing, betta fish are living creatures, not wall decorations. Myself and many others have petitions running to ban these cruel devices from ever being sold. ANYTHING that cannot hold at least a gallon of water is not a good home for a betta fish. Half of a gallon is the absolute minimum.

Secondly, plastic containers can leach small amounts of chemicals into the water they are holding. These small amounts may not be harmful to humans, but compared to a human, a fish is tiny! Even a trace amount of any chemical can kill fish quite quickly (which is exactly why you need to dechlorinate your tap water, which you are doing perfectly.) Acrylic and glass containers are much safer for fish.

Thirdly, many bettas cannot survive at temperatures in the low 60's. They are tropical fish that need heated water. The ideal range for bettas is 75-80 F,  and if the temperature drops into the 65 - 70 range, the betta will lose coloration and stop moving to conserve heat.

So, to sum things up:

Q. Why did all of my previous fish die?
A. They were kept in containers that were MUCH too small for them to survive in, and the plastic that the container was made out of may have leached chemicals into their water. The lack of a heating device weakened their condition.

Q. How can I save my last fish?
A. If you want to see a happy, perky betta, follow these steps.

1.) Buy a 1 - 5 gallon aquarium, some gravel, and a tiny heater.
2.) Rinse everything thoroughly in hot water, then set up the tank.
3.) Fill the tank with water, then add dechlorinator. Turn the heater on.
4.) Once the temperature stabilizes, slowly add your fish. It is normal for bettas to "freak out" when they are first introduced to a new tank.

Here's a guide you can follow for more detailed steps - I'm sure you've heard enough of me! ;)

http://www.wikihow.com/Take-Care-of-a-Betta-Fish

Hope everything helps, and I am sorry for the loss of your previous betta fish.

-Amber Worman