The Best Algae Eaters for a Planted Tank

No animal eats your way out of an algae problem. Algae grows when light and nutrients outrun the plants, and a cleanup crew grazes the last of it once the other work is done. Add a crew for that, and the glass stays clear with far less scrubbing. Add one to rescue a green tank, and the animals either starve in the shade or get buried under algae they cannot keep up with.

So the real question is not which algae eater is strongest. It is which animal clears the kind of algae you have, at the tank size you run, without adding a bioload you cannot carry. Three do most of the work in a planted tank, and each one has a job.

The short version

• For a planted tank, the three best algae eaters are the otocinclus (Otocinclus sp.), the amano shrimp (Caridina multidentata), and the nerite snail (Neritina sp.). Each clears a different algae.
• Match the animal to the algae: nerites scrape green film and spot algae off glass, amanos strip soft and hair algae off plants and wood, and otos graze the brown diatom film that coats a tank in its first months.
• Size the tank first. Otos and amanos want 10 gallons or more; a nerite snail works in 5; a cherry shrimp colony (Neocaridina davidi) grazes biofilm in a 5-gallon nano.
• None of them clears black beard algae or a cyanobacteria sheet. Fix the light hours and the nutrients, then let the crew hold the line.

An algae eater grazes, it does not cure

A tank lit 10 or more hours a day, or one with more food going in than the plants and animals use, grows algae faster than any animal eats it. The fix is upstream: cut the photoperiod to 6 to 8 hours, add fast plants that outcompete algae for nutrients, and feed less. A crew is the finish, not the filter.

That is why the same three animals work in a balanced tank and fail in a broken one. In a tank that is 90 percent right, six otos and a few amanos keep the glass and leaves clean between water changes. In a tank drowning in algae, they cannot make a dent, and you lose the ones that starve. Get the tank close first, then add the crew to hold the last 10 percent.

The otocinclus: the true algae-eating fish

The otocinclus (Otocinclus sp.) is the rare fish that actually eats algae and never touches a healthy plant. It stays under 2 inches, wants a tank of 10 gallons or more, and does best at 72 to 79 F, pH 6.0 to 7.5, and GH 4 to 15. Keep a group of 6 or more; a lone oto hides and fades.

The catch is what it eats. An oto lives on the soft brown diatom film and green biofilm that coats surfaces, and a young tank does not make enough of it. Only add otos to a mature tank, three months old or older, where the biofilm supply is steady. Put six in a two-week-old tank and they starve inside a month, which is the single most common way keepers lose them.

Amano shrimp: the best on soft and hair algae

The amano shrimp (Caridina multidentata) is the strongest algae grazer of the common inverts. It reaches 2 inches, twice the size of a cherry shrimp, which puts it out of reach of most community fish. It suits a tank of 10 gallons or more at 65 to 80 F, pH 6.5 to 7.5, and GH 6 to 15, and a group of 3 or more spreads out to cover more ground.

Amanos work soft green algae and hair algae off plants, wood, and rock better than anything else you can add. They will not breed in a freshwater tank, since the larvae need brackish water, so a group of five stays a group of five with no population boom. The honest limit: an amano fed on flake and pellet leftovers stops working the walls. If you overfeed, it eats the easy food and ignores the algae.

Nerite snails: the glass and film specialists

The nerite snail (Neritina sp.) is the best algae snail that will not overrun a tank. It grows to about 1 inch, works in a tank as small as 5 gallons, and grazes green film and green spot algae off glass and hard surfaces that shrimp tend to leave behind. It holds up at 72 to 82 F and wants harder, alkaline water: pH 7.0 to 8.5 and GH 6 to 18.

Two honest notes. A nerite lays small white eggs around the tank that never hatch in freshwater, so they are a cosmetic nuisance, not a breeding problem. And in soft water under GH 6, its shell pits and erodes, so a nerite is a poor match for a soft blackwater tank. One nerite per 5 to 10 gallons is plenty; a crowd of them runs out of film to eat.

The cherry shrimp colony: cleanup that breeds its own replacements

A cherry shrimp colony (Neocaridina davidi) is not the heaviest algae eater, but it is the cleanup animal that pays for itself. Each shrimp reaches about 1.2 inches, lives in a tank as small as 5 gallons, and grazes biofilm, soft algae, and leftover food all day at 65 to 78 F and GH 4 to 14. Start with 10 or more and the colony breeds to fill the tank.

The trade is fragility. Cherry shrimp need minerals in the water to molt, so GH under 4 is a slow killer, and copper, found in some fish medications and plant fertilizers, wipes a colony fast. In a mature, planted tank with no copper, a colony is the quietest cleanup crew there is, and it replaces its own losses without you buying more.

The crew at a glance

Animal	Latin name	Min tank	Temp	Clears	Note
Otocinclus	Otocinclus sp.	10 gal	72 to 79 F	Brown diatom film, green biofilm	Mature tank only, group of 6
Amano shrimp	Caridina multidentata	10 gal	65 to 80 F	Soft green and hair algae	Will not breed in freshwater
Nerite snail	Neritina sp.	5 gal	72 to 82 F	Green film and spot algae on glass	Needs GH 6 or more
Cherry shrimp	Neocaridina davidi	5 gal	65 to 78 F	Biofilm, soft algae, leftovers	Copper kills it
Ramshorn snail	Planorbella sp.	2 gal	65 to 82 F	Detritus and soft algae film	Breeds to match feeding

The honest part: what a crew cannot fix

No animal here clears black beard algae, the dark tufts that grip wood and slow-plant edges, or a blue-green cyanobacteria sheet. Those are a light-and-flow problem you fix by hand and by cutting the photoperiod, not with a snail. Buying six otos to fight black beard algae just gives you six starving otos.

The other failure is bioload math. Adding a school of 6 otos plus 5 amanos to a 10-gallon that is already stocked can push the tank past what it can process, and the algae you were fighting gets worse from the extra waste. A crew is livestock, not equipment: it eats, it produces waste, and it counts against your stocking. Add it slowly, a few animals at a time, and watch the water. If an animal looks sick after you add it, that is a water-quality or health question for a vet, not a reason to add anything to the tank.

Frequently asked questions

What is the best algae eater for a small tank?

For a tank of 5 gallons, a single nerite snail (Neritina sp.) on the glass plus a small cherry shrimp colony (Neocaridina davidi) is the best pairing. Both work in 5 gallons, neither harms plants, and together they cover glass film, biofilm, and leftover food. Skip otocinclus and amano shrimp in a nano; both want 10 gallons or more.

Do algae eaters get rid of algae completely?

No. Algae is a light-and-nutrient imbalance, and a crew grazes the residue after you fix the cause. Cut the photoperiod to 6 to 8 hours, add fast plants, and feed less; then a crew keeps the clean surfaces clean. An animal added to a green tank cannot out-eat the growth.

Will an otocinclus eat black beard algae?

No. An otocinclus eats soft diatom and green biofilm, not the tough dark tufts of black beard algae. Nothing in a standard cleanup crew reliably clears black beard: you remove it by hand, cut the light, and steady your CO2 or flow. The fish sometimes credited with it, the Siamese algae eater, grows past 5 inches and outgrows most planted nanos.

Can I keep algae eaters with shrimp?

Yes. Otocinclus, nerite snails, and amano shrimp are all safe with a cherry shrimp colony; none of them hunts shrimp. The one rule is copper: keep copper-based medications and copper-heavy fertilizers out of a shrimp tank, because copper that a snail or fish shrugs off will kill a shrimp colony.

Before you buy a cleanup crew, build the tank that makes less algae: the right photoperiod, enough fast plants, and a stocking level the volume can carry. Run your setup through the build planner for a stocked, balanced 10-gallon or 20-gallon, check any animal's real numbers in the compatibility database, and read the rest of the species compatibility guides. If you are stocking from scratch, stocking a 10-gallon tank and the cold-water aquarium fish list are the next two to read; if you keep goldfish, check what goldfish do to plants before you plant anything soft.