Pleco tank: tank size, driftwood and caves

A pleco is an armored catfish with a sucker mouth, and the name covers a whole family of them. Stores sell most kinds at 2 or 3 inches (5 to 8 cm), whether they'll stop at 4 inches or grow past 15, so the species on the tag decides how big a tank you need.

For most tanks, the one to buy is a bristlenose pleco. It stops near 4.9 inches (12.5 cm), TankBud lists 20 gallons (75 liters) as its smallest tank, and one fits a 29 gallon community with room to spare. Give it driftwood to rasp, a cave to hide in and food of its own after dark, because the algae in a tank won't keep a pleco fed.

The common pleco outgrows most tanks

The fish sold as a common pleco is one of several look-alike species. TankBud's common pleco grows to 15.7 inches (40 cm) and lists 100 gallons (379 liters). Most stores now stock farmed sailfin catfish under the same name, though, and the Amazon sailfin catfish reaches 17.7 inches (45 cm) in the same 100 gallons.

They grow fast as well. Many sailfin catfish pass 12 inches (30 cm) by the age of two, and they can live more than 10 years in a tank. A small tank won't hold one back, either, because no fish grows to fit its tank. If a pleco seems to have stopped growing in a small tank, it's stunted, and stunted fish are almost always in poor health.

The stocking calculator reads one adult common pleco as Overstocked in a 55 gallon tank and Heavy in a 75, since both fall under the fish's minimum. In a 100 gallon tank, the same fish reads Full with nothing else in the tank. It takes 125 gallons before it reads Comfortable, and a pleco that size still makes a lot of waste for the filter to carry.

If yours has already outgrown its tank

A bigger filter won't fix a tank that's too small, so the answer is a new home for the fish. Ask the store that sold it first, because shops do take large plecos back. If yours won't, look for another keeper who has a tank of 125 gallons or more.

Which plecos fit which tank

Pick the pleco for the tank you already have. Each fish in the table fits the tank in its row as an adult, going by the smallest tank and the adult size on its species page.

Plecos →126 species

No pleco in the catalog fits a 10 gallon tank. The smallest members of the family are the otocinclus, and the common otocinclus lists 12 gallons (46 liters). Keep otocinclus in a group of six or more, and add them only to a mature tank that already grows algae and biofilm, because they graze all day and can starve in a new one.

From the 40 gallon row on, most of the picks are sold under an L-number. Many of them come from warm, fast-flowing rivers, so check the temperature range on the species page before you buy one.

Since a pleco spends its life on the bottom, the floor of the tank matters more than its height. If you're choosing between two tanks of the same volume, pick the longer, wider one.

A bristlenose in a 29 gallon community

The bristlenose is the usual first pleco because it stays small, takes most foods and is bred commercially, so you won't have trouble finding one. It lists 70 to 79°F (21 to 26°C) and a pH of 6.5 to 7.5, which overlaps most community fish. An adult male grows a beard of fleshy bristles over his snout and head, which is where the name comes from, while a female has a few short ones around her mouth at most.

One bristlenose with eight cherry barbs and six panda cories reads Comfortable in a 29 gallon tank.

A bristlenose under cherry barbs

• 8Cherry barb
• 6Panda cory
• 1Bristlenose pleco

Comfortable

LightComfortableFullHeavyOverstocked

These species overlap at 72–77°F (22–25°C), pH 6.5–7.5.

Open this plan in the stocking calculator

The same pleco fits a 20 gallon tank, where it reads Full beside seven cherry barbs. That's why the 29 gallon tank is the better pick if you'd like room for more fish.

Two bristlenoses read Heavy in a 20 gallon tank and Comfortable in a 29. They're territorial with their own kind, though, and males compete for caves, so a second one needs a cave of its own at the other end of the tank. A male and a female will often spawn without any help from you, and the male guards the eggs in his cave. If you don't want to find homes for the young, keep one.

A clown pleco in a 20 gallon tank

The clown pleco stays at 3.5 inches (9 cm) and lists the same 20 gallons. It's a wood eater, so it needs several pieces of driftwood, and it turns that wood into a steady fall of fine waste that your filter and siphon have to keep up with. One clown pleco with ten ember tetras reads Full in a 20 gallon tank.

A clown pleco with ember tetras

• 10Ember tetra
• 1Clown pleco

Full

LightComfortableFullHeavyOverstocked

These species overlap at 73–82°F (23–28°C), pH 6.6–7.0.

Open this plan in the stocking calculator

Driftwood to rasp

For a pleco, wood is food as well as cover. PlanetCatfish calls driftwood mandatory for a bristlenose, which rasps it for roughage, and the clown pleco and the big royal pleco eat wood as a regular part of their diet. Put at least one solid piece in every pleco tank, and several kinds for a wood eater.

Even a wood eater can't live on wood alone. In a 2009 feeding trial, royal plecos digested less than a third of the cellulose in the wood they ate, and they lost weight on it. That's why every pleco needs vegetables and prepared food beside its wood.

New wood often floats at first and stains the water brown with tannins. Soaking it beforehand takes care of both, as the set-up guide explains.

A cave for every pleco

By day, a pleco tucks itself into the tightest gap it can find, and a male bristlenose spawns in his cave and stays there to guard the eggs. Give each pleco a cave of its own, and add a spare, because it's always worth having more caves than catfish. A good cave is closed at one end and only slightly wider than the fish, since a snug cave is the one it'll use.

Ceramic caves, lengths of PVC pipe, pieces of slate and small flowerpots all work. Set them apart, with wood or rock in between, so that each pleco can hold one without a fight. Under the caves and the wood, use sand or fine gravel.

Strong flow for the warm-water plecos

A bristlenose is happy with the flow in an ordinary community tank, but the fancy plecos from Brazil's Rio Xingu need more. The zebra pleco lists 79 to 86°F (26 to 30°C), and Seriously Fish wants the water in its tank turned over 8 to 12 times an hour, about half of it by the filter and the rest by a powerhead. The gold nugget pleco comes from the same river and lists 81 to 90°F (27 to 32°C). Since warm water holds less oxygen than cool water, give any tank that warm a powerhead or an air stone.

The green phantom pleco likes the same warmth, and it passes the pair check with community fish. One of them with twelve cardinal tetras and eight Sterba's cories reads Full in a 55 gallon tank, and all three share 79 to 82°F (26 to 28°C).

A green phantom pleco in warm water

• 12Cardinal tetra
• 8Sterba's cory
• 1Green phantom pleco (L200)

Full

LightComfortableFullHeavyOverstocked

These species overlap at 79–82°F (26–28°C), pH 6.0–7.0.

Open this plan in the stocking calculator

The bulldog pleco goes the other way. It lists 68 to 77°F (20 to 25°C) and it's marked difficult, so keep it out of a warm community tank.

Whichever pleco you keep, buy a filter rated for a bigger tank than yours, because plecos eat a lot and make a lot of waste. Keeping a pleco isn't a reason to skip the weekly water change, so keep changing a quarter to half of the water every week.

Food after the lights go out

A home tank never grows enough algae and biofilm to support a pleco, so plan on feeding yours every day. Sinking algae wafers make a good staple for a bristlenose, and fresh zucchini or cucumber adds the fiber it needs. If small holes show up in the middle of broad leaves, such as an Amazon sword's, your bristlenose is rasping the plant, and it's time to offer more vegetables.

The diet depends on the species. Once it's past the juvenile stage, the zebra pleco prefers meaty foods such as frozen bloodworms and chopped prawn, and it rarely takes algae. A wood eater needs its wood, with vegetables on the side.

Most plecos are nocturnal, which is why the food should go in after the lights are off, once the faster fish have stopped feeding. To see whether enough is getting through, look at the belly when the pleco sits on the glass. A gently rounded belly means it's eating well, while a hollow belly and sunken eyes are the classic signs of a starving pleco.

Peaceful with fish, territorial with plecos

A bristlenose ignores the fish swimming above it, and TankBud marks it peaceful. Schooling fish that keep to the middle of the tank make easy company, and corydoras share the bottom with it without trouble.

Other plecos are where the friction comes from. Most are territorial with their own species and with plecos of a similar shape, so keep one to a tank unless the tank is big enough for each to hold a cave out of the others' sight.

A shy pleco needs quiet company. The zebra pleco is easily outcompeted for food, which is why it doesn't suit a busy community tank.

Big plecos have also been seen latching onto slow fish such as goldfish and rasping at their sides. TankBud's pair check marks a common pleco with a common goldfish as a caution.

Buying and moving a pleco

Look at the belly in the store too, because newly imported plecos often arrive thin. Pass on any fish with a hollow belly or sunken eyes, and ask to see it eat if you can.

Go gently with the net when you catch a pleco, because the small spines on its fins and cheeks catch easily in the mesh. If you can, scoop it up in a tub instead.

Before the pleco comes home, cycle the tank and put the wood and caves in. Then quarantine the new fish in a spare tank for a few weeks, and use that time to get it eating well.