I think my fish is sick.

Question
QUESTION: Right now, I have a Black Moor Goldfish and a Calico Telescope Goldfish living in a twenty gallon tank. Yesterday, both fish were completely fine, but today, my Calico is just staying at the bottom of the tank not doing anything. I've only had my fish for a little over a week, so I don't know what to do. I tried to look up different types of diseases, but I couldn't find one that I thought fit, so can you please help me?

ANSWER: It could be Hexamita if it stays in a corner. Are there any other symptoms?

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QUESTION: There really aren't any other symptoms. He still eats and everything, but he just lays there. Today, my Black Moor which looked healthier than my Calico died. He looked like he had some white dots on him, but that was the first time I had seen them. When I got home from school, he looked like he was having trouble breathing. I went out and bought the ich medicine, but when I got home, he was already dead. I am now treating my tank for ich, but I'm not positive that that is the problem.
ANSWER: White specks does mean Ich. Continue with the treatment. Is the feces white or a dark color (whie means something is wrong)?

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QUESTION: His feces fluctuates in color. Sometimes it is white, a yellow brown, or a reddish brown color. All these colors are in the goldfish flakes that I feed him.

Answer
It could be Hexamita then. Continue your treatment and if things don't improve, then try this:
Combine metronidazole (1% mixed with food) in the fish's food and in the water (12 mg per liter) is recommended. Repeat the water treatment every other day for three treatments.