Fish... do not get depressed, first of all. Secondly, it's only been a few days, he's just getting used to it. Thirdly, did you cycle the tank beforehand for at least five days? That is crucial. Do you also have a heater, and a filter? Those are also crucial things to have.
Also try to mix up his diet. Feed him flakes, pellets, brine shrimp, blood worms, also try zucchini and cucumber.
Is he in a 5 gallon tank or larger? If he is in a tank less than four gallons, he is cramped. You should fix that immediately.
Also try to mix up his diet. Feed him flakes, pellets, brine shrimp, blood worms, also try zucchini and cucumber.
Is he in a 5 gallon tank or larger? If he is in a tank less than four gallons, he is cramped. You should fix that immediately.