Fish aren't normally my thing, but could this be a Arothron nigropunctatus? I've seen that in another aquarium and this individual looks very similar in color, shape and fins.
Yellow form of Guineafowl Puffer Arothron meleagris. The yellow form of A. nigropunctatus is similar, but this species will have dusky patches around the mouth, gill opening and dorsal fin base. Yellow form A. nigropunctatus usually has a pale belly too.
