Blind Betta

Question
QUESTION: I have a betta in a breeding box inside a 75 gallon tank with three piranahas. The tank is kept at 80 degrees. I noticed two weeks ago that the betta was not swimming, just laying at the bottom of the tank, its eyes were cloudy, wasn'coming to the top of the tank for food anymore, just basically laying there dying. I had stuck my finger inside the box right next to the fish's face and it never even moved away or acted like it had seen me at all. i was wondering if it had went blind and if there was anything i could do to help my betta.
Thanks,
Damien

ANSWER: Damien,
Why on Earth do you have him kept in a breeding box? Get him his own tank, preferably 2 gallons or more. Breeding boxes were meant only for specific kinds of fish who give live birth - bettas not being one of them - and is only used when the fish is pregnant. Even then, it's very stressful on a mother fish and a lot of people won't use breeding boxes because of that.
They are definitely not suitable to house a fish indefinitely. It's simply too stressful.

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QUESTION: It says on the breeding box that it is also made to keep one or two bettas in it and i only have one in it

ANSWER: It also says on bowls that you can put goldfish in them. However, all goldfish grow too large, are too large bodied and create far too much waste and therefore ammonia to ever live out their full lives in a bowl.
Breeding boxes should not be used to house fish indefinitely.
I can guarantee you that if you put him into a proper tank you will see improvement.


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QUESTION: do i just put him in a regular bowl with no filter or anything?

Answer
I usually suggest a small two gallon or larger tank. A filter and aeration are not necessary, though if you do end up adding more fish you'll want to get a filter. I do recommend a heater unless you usually keep your house in the mid 70's (most people don't). You can get a small 7.5 watt mini tank heater from some pet stores - like Petco.
You can most certainly do a bowl instead if that is what you wish, but for optimum health and a longer lifespan, a two gallon would be much better.
If you want to try and tempt him into eating, you might try some blood worms.
You might also check the ammonia and nitrite levels in your main  tank just to be doubly safe.