They are small fish, all less than  in adult length, and are distinguished by their habitual head-down postures.
ðeɪ ɑːɹ smˈɔːl fˈɪʃ, ˈɔːl lˈɛs ðɐn ɪn ɐdˈʌlt lˈɛŋθ, ænd ɑːɹ dɪstˈɪŋɡwɪʃt baɪ ðɛɹ hɐbˈɪtʃuːəl hˈɛddˌaʊn pˈɔstʃɚz.