When this is exhausted some move on to feed on bacteria, algal crusts, detritus and raspings from submerged plants.
wˌɛn ðɪs ɪz ɛɡzˈɔːstᵻd sˌʌm mˈuːv ˌɔn tə fˈiːd ˌɔn bæktˈɪɹiə, ˈælɡəl kɹˈʌsts, dᵻtɹˈaɪɾəs ænd ɹˈæspɪŋz fɹʌm səbmˈɜːdʒd plˈænts.