| Odessa barb Barbus sp. Odessa |  |
| Oligancistrus sp. Polka Dot Oligancistrus sp. L020 |  |
| One-spot catfish Synodontis notatus |  |
| Ornate bichir Polypterus ornatipinnis |  |
| Ornate tetra, False rosy tetra, Bentos tetra, White-tipped tetra Hyphessobrycon bentosi |  |
| Oscar, Velvet cichlid Astronotus ocellatus |  |
| Oto, Midget suckermouth catfish, Dwarf sucker catfish Otocinclus affinis |  |
| Oligancistrus sp. L020 Oligancistrus sp. Polka Dot | |
| Oryzias latipes Rice fish | |
| Otocinclus affinis Oto, Dwarf sucker catfish, Midget suckermouth catfish | |
Vegetarian fish Some catfish have a largely vegetarian diet; feed them potato, lettuce, cucumber or blanched peas. Some of these will have to be weighted down, or held in place with a commercially available lettuce grip (magnetic clips are far better than suction types). As with all fish, do not over feed; remove uneaten vegetable matter after a couple days