ya..i agreed with weirdfishlover it maybe still new to the environment. just provide good water , a drift wood to hide, give food before lights off , clear left over in the morning. if there are other competitors in the tank..then do "home delivery" to it.
Very nice pick up especially at that price. You got hooked up! As for how long it can go without eating...that depends on alot of factors; health, condition, infections, stress, resilience, will to live....but a solid answer is until it dies!