Algae eaters compared: shrimp, snails, and fish that work
Updated October 2026
Pick an algae eater by the algae you already have, not by the species that looked busiest at the store. Nerite snails clear diatoms and green spot. Amano shrimp work through soft hair and thread algae. Siamese algae eaters are the common option that will actually graze black beard algae.
Buy the wrong one and you add bioload to a tank with the same green glass.
Match the species to the algae you have
Adult sizes below are the figures published in standard species references. Minimum tank sizes reflect swimming room and territory rather than filtration capacity.
| Species | Algae it targets | Published adult size | Minimum tank |
|---|---|---|---|
| Nerite snail (Neritina spp.) | Diatoms, green spot algae | 2.5 cm | 5 gallons |
| Amano shrimp (Caridina multidentata) | Hair and thread algae, biofilm | 5 cm | 10 gallons |
| Otocinclus (Otocinclus spp.) | Diatoms, soft green film | 4 cm | 10 gallons |
| Bristlenose pleco (Ancistrus sp.) | Soft green film, leftover food | 12 cm | 25 gallons |
| Siamese algae eater (Crossocheilus oblongus) | Black beard algae, hair algae | 14 cm | 30 gallons |
How each one behaves once it settles in
Nerites work glass and hardscape hard, and they lay hard white eggs on driftwood that will not hatch in freshwater. If the egg specks bother you, keep one instead of four. Full detail sits in our nerite snail care guide.
Video: Cichlid Bros
Amano shrimp are the strongest soft-algae grazers in the hobby, and they stop grazing the moment you overfeed. Cut back on pellets for a week and they go back to the algae. Our amano shrimp care guide covers molting and the copper problem.
Siamese algae eaters graze hardest as juveniles and slow down past 10 cm. Buy them young, keep three or more, and expect them to lose interest in black beard algae once they learn where the prepared food lands.
Tank size sets your shortlist before anything else
Under 10 gallons you have two real options: nerites and amano shrimp. A siamese algae eater in a nano tank is a fish you will rehome within a year, which is why it does not appear in our best nano tanks for aquascaping picks.
Otocinclus sit in between. They need established biofilm to graze, so they starve in setups younger than two months.
Stocking density decides the result more than species count does. One amano per 2 gallons is a sensible starting point, and going heavier mostly gets you shrimp competing for the same patch of hair algae.
What none of them fix
Algae eaters graze what has already grown. They do not shorten your photoperiod, drop your nitrate, or steady a CO2 swing.
If your tank grows algae faster than a cleanup crew can eat it, the crew is not the lever you are looking for. Cut the light duration first, then restock.
Questions readers ask
Which algae eater handles black beard algae?
Siamese algae eaters are the one commonly available species that grazes black beard algae, and they do it most reliably while still juvenile. Amano shrimp and nerite snails largely ignore it. Treat the cause as well, since black beard algae usually tracks unstable CO2 or poor flow.
How many algae eaters do I need for a 20 gallon tank?
Around 10 amano shrimp or 2 to 3 nerite snails suits a 20 gallon planted tank. Add them gradually rather than all at once, because a fully stocked cleanup crew in a tank with little algae simply goes hungry.
Can algae eaters live together in the same tank?
Yes, and mixing them is usually better than stocking one species heavily, since each targets different algae. Nerite snails, amano shrimp and otocinclus coexist without conflict. Keep copper-based medications out of any tank holding shrimp or snails.
