Bristlenose pleco vs otocinclus: which should you choose?
AquaLog guide · Published
In short: Choose a bristlenose pleco, a beginner-rated algae eater usually kept singly, if your tank holds at least 110 L (29 US gal); choose otocinclus for a mature planted tank of 60 L (16 US gal) or more, in a group of six or more. They can share a tank at 22–27 °C (72–81 °F) and pH 6–7.5 if both get vegetable food. Skip the common pleco unless you have at least 700 L (185 US gal).
How do they compare?
| Bristlenose pleco | Otocinclus | |
|---|---|---|
| Minimum tank | 110 L (29 US gal) | 60 L (16 US gal) |
| Temperature | 22–28 °C (72–82 °F) | 21–27 °C (70–81 °F) |
| pH | 6–7.8 | 6–7.5 |
| Hardness | 2–20 dGH | 2–15 dGH |
| Adult size | 13 cm (5.1 in) | 4 cm (1.6 in) |
| Temperament | Peaceful | Peaceful |
| Group size | Kept singly | 6 or more |
| Care level | Beginner | Intermediate |
| Lifespan | 5–12 years | 3–5 years |
| Diet | Herbivore: algae wafers, courgette, driftwood to rasp | Herbivore: soft green algae, biofilm, blanched courgette |
| Where it swims | Bottom | All levels |
All figures come from our care guide: see bristlenose pleco and otocinclus. Courgette is zucchini.
What is the real difference?
Size and lifestyle. The bristlenose is a single 13 cm (5.1 in) catfish that rasps algae and wood and needs 110 L (29 US gal). Otocinclus are 4 cm (1.6 in) grazers that live in groups and fit a 60 L (16 US gal) tank. Our care guide rates the bristlenose beginner and the otocinclus intermediate, and notes that otos are fragile in a brand-new setup and suit a mature planted tank.
Choose a bristlenose pleco if…
- Your tank is 110 L (29 US gal) or larger and you want one algae eater.
- You keep larger community fish. Our data lists most community fish, angelfish and rainbowfish as good tank mates.
- You can offer driftwood and vegetables. Its diet includes wood to rasp, algae wafers and courgette.
- You'd like to breed something. Our data rates its breeding intermediate, against advanced for otocinclus, and notes that males guard the eggs inside caves.
Keep one male per small tank; our data lists another male as a tank mate to avoid, along with aggressive cichlids.
Choose otocinclus if…
- Your tank is at least 60 L (16 US gal) but under 110 L (29 US gal), and it is mature and planted, with soft green algae and biofilm to graze.
- You keep small, peaceful fish. Good tank mates include neon tetras, corydoras, cherry shrimp and rasboras.
- You can keep six or more. Otos are group fish; the bristlenose is not.
- Your tank has no cichlids, bettas or predatory fish. All three are on the oto's avoid list.
Can bristlenose plecos and otocinclus live together?
Yes. Their ranges overlap at 22–27 °C (72–81 °F), pH 6–7.5 and 2–15 dGH. Both are peaceful, the bristlenose lists most community fish as good tank mates, and neither appears on the other's avoid list. Plan on at least the larger minimum, 110 L (29 US gal). The aquarium stocking checker runs the same checks for the rest of your stock.
The catch is food. Both are herbivores, and starvation is a common problem in both records: otos in algae-free tanks, bristlenoses without vegetable food. Two kinds of grazer use up the algae sooner, so feed algae wafers and blanched courgette and check that the otos are eating too, not just the pleco.
And the common pleco?
Our care data says the common pleco is sold at 5 cm (2 in) but reaches 45 cm (17.7 in), needs at least 700 L (185 US gal), lives 10–20 years and produces enormous waste. It is territorial, rated intermediate, and lists nano fish and slow, flat-bodied fish (whose slime coat it may rasp) as tank mates to avoid. Stunting in small tanks is one of its common problems. Its water range is broad: 22–30 °C (72–86 °F), pH 6.5–8 and 4–20 dGH. Its size is the problem.
Unless your tank is that big, choose a bristlenose for algae in a home aquarium, or otocinclus for a small planted one. Check your tank's real volume with the aquarium volume calculator, and compare more options in bottom-dwelling aquarium fish.
Already logging your tanks in AquaLog? Its "Will it fit your tank?" check compares any of these three with your tank's size, water type and latest temperature and pH.