My Betta is very sick!

Question
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Followup To
Question -
My dear Doctor! You are my last hope.I have my Beta for about 7 months.It was very healty and a happy fish.I change water every 3-5 days. I fed it with liver and suddenly it get smaller and smaller,not swiming around,it came very skiny and not eating at all.It color was blue marine and now is lighter and became some kind of yellow and greenish colour.
What can i do for it?
Answer -
Hi Betty;

What size tank does he have?
What is the water temperature?
Does he get other foods besides liver?

Let me know as soon as you can.....

Chris Robbins
ANSWER:
HELOO my dear Doctor!!! It has a standard little tank of 1 gallon of water.The temperature of the water is almoust every time 21-24 Celzius.
He is not getting any other food,he dont like it.He like just liver.

Answer
Hi Betty;

Poor guy. It's possible he has an internal infection of some kind. It could be parasites or even a bacterial infection. If he has become extremely thin and pale he isn't strong enough to treat with an internal parasite medicine so first try some "Maracyn 2", or see if your local fish store has a medication with Kanamycin in it. These two medicines are the only ones that absorb inside the fish. Parasite medicines are risky to use in very sick animals. The cure can actually kill them. Here is a web page about using medicines in small tanks;

http://www.healthybetta.com/easymeds.html

He needs his water warmer too while he is sick. Get it up to 26 to 28 celsius. It really should be no lower than 24 the rest of the time anyway. Put a desk lamp near his tank or another heat source.

A diet of liver is certainly not good. There are toxins in liver as well as far too much protein. He needs fiber and other nutrients in order to be healthy. If he survives this illness, feed a tiny bit of liver but keep offering him  regular betta pellets and peeled green peas. Keep cutting back on the liver until he eats the pellets and peas. He just can't be a healthy fish on just liver.

I hope he feels better soon.....

At Your Service;
Chris Robbins