Best algae eaters by tank size, including betta tanks

The best algae eaters for most freshwater tanks are nerite snails, amano shrimp, otocinclus and the bristlenose pleco. Pick by tank size: a nerite snail for small tanks from 5 gallons (19 L) and for betta tanks, amano shrimp from 10 gallons (38 L), a group of 6 otocinclus or one bristlenose pleco from 20 gallons (76 L), and a Siamese algae eater for black beard algae from 55 gallons (208 L). Skip the common pleco and Chinese algae eater, which outgrow most tanks, and remember that no algae eater fixes the extra light and nutrients that cause algae.

The best algae eaters graze the type of algae you actually have and still fit your tank as adults. For most home aquariums that means nerite snails, amano shrimp, otocinclus or a bristlenose pleco. The wrong pick starves in a spotless tank, eats your shrimp or grows into a 16-inch problem.

Sizes, minimum tanks and temperatures for the snails, shrimp and fish below come from our species data, the same numbers the stocking calculator uses.

Best algae eaters at a glance

Algae eater	Adult size	Minimum tank	How many	Eats best	Temperature
Nerite snail	About 1 in (2.5 cm)	5 gal (19 L)	About 1 per 5 gal (19 L)	Green spot algae, film on glass, rock and wood	72–81 °F (22–27 °C)
Cherry shrimp	1.2 in (3 cm)	5 gal (19 L)	Colony of 10+	Biofilm, soft film algae, leftovers	68–81 °F (20–27 °C)
Amano shrimp	1.8 in (4.5 cm)	10 gal (38 L)	3 or more	Hair and thread algae, some black beard algae	68–81 °F (20–27 °C)
Otocinclus	1.6 in (4 cm)	20 gal (76 L)	6 or more	Brown diatoms, soft green film	70–79 °F (21–26 °C)
Bristlenose pleco	4.7 in (12 cm)	20 gal (76 L), 24 in (60 cm) long	1	Film algae and diatoms on glass, wood and rock	72–79 °F (22–26 °C)
Rubber lip pleco	5.5 in (14 cm)	29 gal (110 L), 4 ft (120 cm) long	1	Film algae on rocks, wood and glass	70–77 °F (21–25 °C)
Siamese algae eater	5.9 in (15 cm)	55 gal (208 L), 4 ft (120 cm) long	1, or 3 or more	Hair algae and black beard algae, mainly while young	72–79 °F (22–26 °C)

Amano shrimp, cherry shrimp and the bristlenose pleco are rated easy in our data. Otocinclus, the rubber lip pleco and the Siamese algae eater are rated moderate, because they need a mature tank, cooler fast water or a lot of space. Nerite snails are hardy, but they need hard, mineral-rich water with a pH of 7 or above, or their shells erode.

Match the algae eater to your algae

No animal eats every kind of algae. Name yours first. Our algae guide explains how to identify each type and fix what causes it.

Algae	What it looks like	Best eaters	Notes
Brown diatoms	Brown dust on glass, sand and leaves that wipes off easily	Otocinclus, nerite snails, bristlenose pleco	Common in the first few months and often fades as the tank matures
Green spot algae	Hard green dots on the glass and on slow-growing leaves	Nerite snails	Shrimp and otocinclus mostly ignore it. Scrape glass with a blade, acrylic with a plastic card
Soft green film	Green haze on the glass that wipes off with a finger	Bristlenose pleco, nerite snails, otocinclus	Grazers keep it down well in a tank with balanced light
Hair and thread algae	Fine green strands on plants and decor	Amano shrimp, young Siamese algae eaters	Pull out the bulk by hand, then let the grazers handle regrowth
Black beard algae	Dark gray to black tufts on leaf edges, wood and equipment	Young Siamese algae eaters; amano shrimp nibble it	Most algae eaters ignore it. Nerites rarely touch it unless they are starving
Green water	Cloudy, pea-green water	None	Free-floating algae can’t be grazed. Cut the light and fix nutrients, or use a UV sterilizer
Blue-green “algae”	Slimy dark green or blue-green sheets that peel off, often with a musty smell	Almost none	It is a bacterium, not algae. Improve flow, clean the gravel and feed less

Best algae eaters by tank size

Small tanks have less algae to feed grazers and less room for their waste, so stock the cleanup crew as carefully as the fish.

Algae eaters for a 5 gallon tank (19 L)

Nerite snail: the best pick. One is enough for a 5 gallon tank, and it can’t overrun the tank, because its eggs need brackish water to hatch.
Cherry shrimp: a colony of 10 suits a 5 gallon shrimp-only tank, though 10 gallons (38 L) is easier to keep stable. They graze biofilm and leftovers rather than clearing visible algae.
Skip: amano shrimp (10 gallon minimum), otocinclus (20 gallons) and every pleco.

In a 3 gallon (11 L) tank, none of these animals meets the minimum tank size in our data. Keep algae down there with a shorter light period and a quick wipe of the glass at each water change.

Algae eaters for a 10 gallon tank (38 L)

Three amano shrimp plus one or two nerite snails cover hair algae, film algae and green spot algae between them. In our stocking calculator, 8 ember tetras with 3 amano shrimp use only 26% of a 10 gallon tank.

Otocinclus are often sold for 10 gallon tanks. In our data a group of 6 needs 20 gallons (76 L), and a small tank rarely grows enough algae to feed them, so underfed otos often die in their first few weeks.

Algae eaters for 20 to 29 gallon tanks (76–110 L)

Bristlenose pleco: the best all-round algae fish for home tanks. It stays around 4.7 in (12 cm), grazes glass and wood day and night, and is safe with shrimp, though some nibble soft plants. Give it driftwood and a cave, and drop in wafers after lights out.
Otocinclus: a group of 6 in a mature, planted tank. They are the best grazers for brown diatoms on delicate leaves, but they are fragile in a new or bare tank.
Add-ons: two or three nerites for green spot algae and a few amano shrimp for hair algae.

In our calculator, 10 neon tetras with 6 otocinclus fill 52% of a 20 gallon tank. In a 29 gallon, 10 harlequin rasboras with 1 bristlenose and 4 amano shrimp fill 52%.

Skip the rubber lip pleco here. It needs a tank about 4 ft (120 cm) long, and a standard 29 gallon is only 30 in (76 cm).

Algae eaters for 40 gallons and up (151 L+)

Rubber lip pleco: a good fit for a 4 ft (120 cm) tank, such as a 40 gallon long or a 55 gallon, with strong flow and cooler water, 70–77 °F (21–25 °C). A 40 gallon breeder, at 36 in (91 cm), is short of that. Skip it in warm tanks for discus, rams or bettas.
Siamese algae eater: the best fish for black beard algae while it is young. Keep one in 55 gallons (208 L) and 4 ft (120 cm), or a group of 3 or more in about 80 gallons (304 L) and 5 ft (150 cm). Avoid exactly two, as a pair often fights. Adults may eat cherry shrimp and other dwarf shrimp.
Bristlenose pleco: still a good choice, but our checker gives a caution with a Siamese algae eater, because a bristlenose may chase other fish that rest near its cave.

Example cleanup crews

Tank	Cleanup crew	Goes well with
5 gal (19 L)	1 nerite snail	A betta, or a cherry shrimp colony
10 gal (38 L)	1–2 nerite snails + 3 amano shrimp	Nano fish such as ember tetras
20 gal (76 L)	6 otocinclus or 1 bristlenose pleco, plus 2 nerite snails	Small tetras and rasboras, or a betta
29 gal (110 L)	1 bristlenose pleco + 4 amano shrimp + 3 nerite snails	Peaceful community fish
55 gal (208 L)	1 Siamese algae eater + 4–6 nerite snails	Active fish of similar size, no dwarf shrimp

Best algae eaters for betta tanks

A betta narrows the list. Many bettas hunt anything small that moves, and they need warm water, 75–82 °F (24–28 °C), which rules out cool-water grazers.

Algae eater	With a betta	Shared temperature	Tank needed
Nerite snail	Good, the safest pick	75–81 °F (24–27 °C)	5 gal (19 L)
Otocinclus (6)	Good	75–79 °F (24–26 °C)	20 gal (76 L)
Bristlenose pleco	Good	75–79 °F (24–26 °C)	20 gal (76 L)
Amano shrimp	Caution: many survive, but expect some losses	75–81 °F (24–27 °C)	10 gal (38 L)
Rubber lip pleco	Caution: needs cooler water than a betta	75–77 °F (24–25 °C) only	Not a good match
Cherry shrimp	Avoid: many bettas hunt them	75–81 °F (24–27 °C)	Keep them in their own tank
Chinese algae eater	Avoid: adults may latch onto the betta	75–79 °F (24–26 °C)	Not a good match

If you try amano shrimp with a betta, add the shrimp first and the betta a week or two later, and plant the tank densely so molting shrimp can hide. Larger mystery snails are riskier than nerites, because a betta may peck at their long feelers. See every safe option on our betta tank mates page, or test your exact mix in the compatibility checker.

Algae eaters to avoid

These are sold as small tank cleaners. Each grows far bigger, or meaner, than the tag suggests.

Sold as	Adult size	What it really needs	Choose instead
Common pleco	About 16 in (40 cm), sometimes more	150 gal (568 L), 6 ft (180 cm) long, for 10–20 years	Bristlenose pleco
Chinese algae eater	About 8 in (20 cm), sometimes more	One fish in 80 gal (304 L), 5 ft (150 cm) long	Siamese algae eater (55 gal and up) or bristlenose pleco

Common pleco. Put one adult in a 20 gallon tank in our stocking calculator and it fills 231% of the waste budget and 116% of the swimming room on its own. Adults also eat less algae than babies, and a hungry one may rasp the slime coat off slow, flat-sided fish such as angelfish, discus and goldfish. Released plecos have turned up in waterways across the southern US and other warm regions, where some breed and dig nesting burrows that erode riverbanks. Never release one. Ask a fish store or club to rehome it.

Chinese algae eater. Young fish graze quietly, but adults turn territorial. They chase bottom fish and look-alikes, and may latch onto the sides of slow, flat-sided fish to feed on their mucus. Seriously Fish calls it largely unsuitable for a general community tank. It also eats dwarf shrimp.

How to tell the look-alikes apart:

Siamese algae eater: clear fins, and a black stripe that runs all the way to the tip of the tail.
Flying fox: a thin gold line along the black stripe, and black marks on the fins.
Chinese algae eater: a large sucker-disk mouth, with a brown body and a bumpy dark stripe, or an all-gold body.

Algae eaters don’t replace maintenance

Algae grows when light and nutrients outpace what your plants use. Grazers trim the visible growth, but every animal adds waste that feeds the next round, so fix the cause first:

Run the light 6–8 hours a day on a timer, and keep the tank out of direct sun.
Feed only what the fish finish in a minute or two. Leftovers break down into the nutrients algae uses, and algae eaters fill up on them instead of grazing.
Change 25–30% of the water weekly and keep nitrate below 40 ppm, ideally 20 ppm or less. Our water change guide shows how to tune the amount.
Add fast-growing stem or floating plants to compete with algae for nutrients.
Add algae eaters a few at a time, then wait about a month to see what they clear before adding more.

How to keep algae eaters alive

Add them to a mature tank. Snails and shrimp need a fully cycled tank. Otocinclus need a tank that has run for a few months and has visible algae and biofilm.
Buy healthy animals. Otos and plecos should have rounded bellies. Snails should cling to the glass, not lie loose on the bottom of the store tank.
Acclimate shrimp and snails slowly. Drip tank water into their container over 1–2 hours, because sudden changes in water chemistry can cause failed molts in shrimp.
Fit a tight lid. Amano shrimp and nerite snails climb out along cords and tubing, and Siamese algae eaters jump.
Read every label before you dose. Copper kills most shrimp and snails, and fenbendazole dewormers and many planaria treatments kill snails. Check medicine labels for these ingredients, choose plant fertilizers labeled safe for shrimp, and follow every label exactly. Treat sick fish in a separate hospital tank so the cleanup crew isn’t exposed, and ask an aquatic vet if you’re not sure what’s wrong.
Feed them on purpose. Use sinking algae wafers and blanched zucchini or green beans once the algae runs low, and feed plecos after lights out.
Add minerals in soft water. Snails and shrimp need calcium for shells and molts. Crushed coral or a mineral supplement, dosed as the label says, helps if your GH is low. Crushed coral also raises KH and pH, so check that suits your fish.

Common mistakes

Buying too many grazers. They strip the algae and then go hungry. About one nerite per 5 gallons (19 L) is plenty.
Mixing cherry shrimp with a betta or a Siamese algae eater. Both eat dwarf shrimp, while bristlenose plecos and otocinclus leave them alone.
Keeping two male bristlenose plecos in a small tank. Males fight over caves. Keep one male unless the tank is large, with several hides.
Panicking over white dots on the decor. In a tank with nerites, they are usually egg capsules. They won’t hatch in fresh water, and you can scrape them off glass and hard decor with a blade.

Gear mentioned in this guide

Algae wafers (opens Amazon in a new tab)Sinking food for plecos, otocinclus and other grazers. How to choose
Algae scraper or magnet cleaner (opens Amazon in a new tab)Use a plastic blade on acrylic tanks: metal scratches. How to choose
Outlet timer for the light (opens Amazon in a new tab)A steady 6–8 hours of light a day is the easiest way to limit algae. How to choose

Product links go to Amazon search results. As an Amazon Associate we earn from qualifying purchases, at no extra cost to you. Disclosure.

Frequently asked questions

What is the best algae eater for a betta tank?

A nerite snail is the safest choice. Bettas rarely bother it, it eats the green spot algae that shrimp and otocinclus ignore, and its eggs don't hatch in fresh water. In 20 gallons (76 L) or more, a group of 6 otocinclus or one bristlenose pleco also gets along well with most bettas.

What eats black beard algae?

Young Siamese algae eaters are the best fish for it, and a group of amano shrimp will pick at it too. Neither clears a heavy outbreak alone, so also trim the worst leaves and fix the cause, which is often a buildup of waste or, in CO2-injected tanks, CO2 levels that swing during the day.

Do algae eaters need to be fed?

Yes. Once the algae runs out they starve, so add sinking algae wafers or blanched zucchini a few times a week for snails and shrimp, and daily for otocinclus and plecos. A sunken belly on an oto or pleco means it is underfed.

Will a pleco keep my tank clean?

No. A pleco grazes algae and leftover food, but it adds a lot of waste of its own and removes no nitrate. You still need weekly water changes, gravel vacuuming and a filter clean now and then.

Will algae eaters eat my plants?

Nerite snails, amano shrimp, cherry shrimp and otocinclus leave healthy plants alone. Bristlenose plecos and Siamese algae eaters sometimes nibble soft leaves, and adult common plecos eat or uproot most plants.