Yes, MOONFISHES is a Scrabble word!

Letter values in Scrabble US: M 3, O 1, O 1, N 1, F 4, I 1, S 1, H 4, E 1, S 1.

Is it a valid word?

MOONFISHES is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

any of several silvery marine fishes with very flat bodies
large elliptical brightly colored deep-sea fish of Atlantic and Pacific and Mediterranean

Also: atlantic moonfish, horse-head, selene setapinnis, lampris regius.

Not playable in Scrabble US: HORSEFISH, HORSEHEAD, DOLLARFISH.