Dear candidate

Depending on the type of piranha these fish generally live in the water with low pH value so, normal tap water that is available for our is alkaline with more pH value which should be avoided for that so, the pH required for Piranha fish is 6.5 and 7.8 and the aquarium temperature should 75 degree to 80 degree F and if the room temp is less than the specified temperature use aquarium heater to increase the temperature of aquarium and you need to filter the water i.e., 10 percent of the water should be changed weekly and note that you need to keep a safe lid on the aquarium to avoid your piranha jumping out of the aquarium and always provide it with steady currents Piranhas when living in the wild or out in the seas or other water bodies they will have a different kind lifestyle or verity diet but it will be different for those same ones in the aquarium so, i am mentioning few types of food to feed your baby piranha

• Fish
• Shrimp
• Mammals like small one like baby rats
• Insects that are live and not diseased or dead like crickets, meal worms, mosquito larvae etc.,
• Worms, safe and live worms which dont have any disease
• Frozen foods, there are the one that are specially made to feed fish which you can buy in pet store
• Frozen cubes like feozen meat like mainly small fish and other meat
• Pellets/ sticks/ flake food like foods with low in protein, calcium and vitamins like very light food
• Meaty foods like beef, beef heart etc., but you need to feed then very small portions

But note that never feed your baby piranha fish the foods like hamburgers,  bacon, sausages, Turkey and fried or fast foods these may harm your piranha fish health because these foods contain spices and so never feed your fish these kind of foods and as you said that your piranha is a baby it need to be fed 2 to 4 times a day.

Hope this Information is helpful