L012 Gainsboro Pleco (Ancistomus feldbergae)

Choose the L012 Gainsboro Pleco from the Rio Xingu

The L012 Gainsboro Pleco is Ancistomus feldbergae, a suckermouth catfish from the rocky rapids of the Rio Xingu in Pará, Brazil. Brazilian scientists described it in 2012 as Peckoltia feldbergae from Ilha de Babaquara, upstream of Altamira, and three years later it was moved to the genus Ancistomus. Planet Catfish lists the common name Gainsboro Pleco, after a pale grey shade, and notes that the trade code L013 is simply a young L012.

The species honours Dr Eliana Feldberg of the Instituto Nacional de Pesquisas da Amazônia, for her work on the cytogenetics of Amazon fish. For a UK fishkeeper the L012 is a peaceful, mid- to large-sized pleco of about 17–20 cm that wants warm, oxygen-rich, flowing water, rock piles and wood, and a territory of its own.

Check the names on the label

In 2015 Armbruster, Werneke and Tan, writing in ZooKeys, recognised Ancistomus as a valid genus and moved this species into it alongside the L141 Ghost Pleco, Ancistomus snethlageae. Its former genus-mates are in our Peckoltia plecos category.

Recognise a true L012

The original description, summarised by FishBase, identifies it by dark brown dots over the whole body, an orange band on the outer edge of the dorsal and tail fins, and thin dark stripes in the dorsal-fin membranes, parallel to the fin rays, that break up into small dots in larger fish. Planet Catfish photographs show a pale beige-grey to yellowish body with these dark spots.

The sources disagree about its look-alikes. Planet Catfish says L012 and L013 are both very similar to L163 from the Rio Tocantins. Seriously Fish places L163 in the Rio Pará, treats L013 as a separate undescribed fish, and says the two are only easily told apart as they mature, because L163 keeps its spots while L013 becomes duller. Buy by the code and the scientific name together, and expect the pattern to change as the fish grows.

Learn from its wild habitat

FishBase, drawing on the original description, records it in shallow river rapids with a bottom of small to medium-sized flat rocks, up to about 50 cm across, over coarse sand and pebbles. The fish hide under the rocks by day and come out at night to graze the film of algae and tiny organisms on the upper surfaces of the stones. The IUCN Red List rates it Least Concern (2018): as ScotCat summarises, it is widespread and abundant in the Xingu basin upstream of Belo Monte, and the Belo Monte dam affects only about 12% of its range.

Turn the habitat into set-up rules

• Flat rocks to hide under: slate or flat stones laid over a soft floor, with gaps beneath them.
• A coarse sand and pebble floor: soft enough for barbels, rough enough to look natural.
• Moving, oxygen-rich water: a current across the rocks and a rippling surface.
• Night-time feeding: food goes in after lights-out, when the fish naturally forages.

Know exactly what you receive

One purchase supplies one live L012 Gainsboro Pleco. The size option is "Standard": the fish is sent at the size currently available, normally a juvenile well below the adult size, which is why some young fish are still sold as L013. Sex is not chosen or guaranteed.

The photographs show the species, not the individual you will receive. Spotting, background colour and the orange fin edges vary between fish and change as they grow.

Plan the group before you order

• One fish: the simplest choice for a community aquarium.
• More than one: Planet Catfish calls the species peaceful if a little territorial and suggests about a 30 cm square of broken-up floor per fish.
• A mix of plecos: give each its own refuge; Seriously Fish expects some territorial confrontations in similar Ancistomus.

Before you order, read our delivery and Live Arrival Guarantee information, and have the aquarium matured, heated and furnished with caves before the fish arrives.

Plan the aquarium around a 17–20 cm adult

FishBase gives a maximum of 17.1 cm standard length and ScotCat 17 cm; Planet Catfish gives 200 mm standard length. Standard length excludes the tail fin, so plan for a solid pleco of about 17–20 cm plus tail.

No minimum aquarium size has been published for this species. Planet Catfish's guide of about a 30 cm (12 in) square of floor per fish, well broken up with décor, is the best species-specific rule. For overall size, Seriously Fish recommends a base of 120 × 45 cm, about 243 litres, for the 16 cm snowball pleco; the L012 grows a little larger, so treat that as a minimum.

Run a three-step space check

1. Measure the base: at least 120 × 45 cm, longer for more than one pleco.
2. Divide the floor: roughly a 30 cm square of rocks and caves for each pleco, separated by rock piles or wood.
3. Work out the true volume: our tank volume calculator turns your dimensions into litres for choosing the filter and heater.

Keep the tank away from radiators, windows and draughts, fit a lid, and run a heater all year round.

Build rock piles and wood tangles

Planet Catfish recommends rock piles and wood tangles and says plants are not vital. That suits the wild habitat: flat stones to hide under, wood for shade and grazing, and a soft floor of sand or fine gravel. Well-fed fish do not damage most plants, Planet Catfish adds, so you can add greenery if you like.

Divide the floor by function

Use sand or fine gravel, because OATA notes that catfish barbels are sensitive and need a soft bottom. Stand the bottom rocks on the glass before adding sand so the stacks stay stable, and check that no flat stone can slip and trap a fish underneath.

Keep the lighting soft and leave shaded areas, so the fish feels safe enough to come out in the evening.

Keep the water warm and rich in oxygen

Planet Catfish gives 25–30°C. ScotCat gives 25–29°C and pH 6.0–7.5 and says the species should be kept slightly warmer than average and needs a higher oxygen level. We suggest 26–29°C, inside both ranges, with strong aeration.

Match your water to the targets

UK tap water differs from region to region, so test yours rather than guess. If it is hard and alkaline, blend it with reverse-osmosis water to bring the pH into range, and then keep the blend the same at every change: a stable reading matters more than a perfect one. Treat every water change with a conditioner to remove chlorine or chloramine. Our water matcher checks your readings against this fish's range, and our water chemistry guide explains each value.

Filter for oxygen, flow and clean water

ScotCat's note about a higher oxygen requirement is the key to filtration. Seriously Fish's guidance for rapids plecos is a filter turning over four to five times the tank volume each hour, extra water movement from a powerhead or air stone where needed, and weekly water changes of 30–50%.

Follow a weekly routine

1. Test ammonia, nitrite, nitrate and temperature.
2. Change 30–50% of the water with conditioned water at tank temperature; OATA's minimum is 25% a week.
3. Siphon the sand and the gaps under the flat stones.
4. Check that the flow still reaches every cave and the surface keeps rippling.
5. Rinse filter media only in old tank water, never under the tap.

In summer, when the room warms up, check the temperature more often: warm water holds less oxygen, and an oxygen-hungry pleco feels it first. Our aquarium filtration guide explains how to combine filters and powerheads.

Feed both plant foods and meaty foods

The wild diet and the aquarium advice differ. FishBase reports that diatoms made up 83% of the stomach contents of two wild fish, with sponge fragments and fine sediment, and that the very long intestine, nearly 11 times the standard length, points to a mainly herbivorous diet. In aquariums, Planet Catfish describes it as omnivorous with a tendency towards meaty foods and not an effective algae eater, while ScotCat lists vegetable food, tablets and pellets, insect larvae, zooplankton and soft wood. Feed both kinds of food, and do not rely on it to clean algae.

Build one measured meal

• Plant base: a sinking vegetable or spirulina tablet most evenings.
• Meaty food: thawed bloodworm, mosquito larvae or other small frozen foods a few times a week.
• Soft wood: a piece of bogwood to rasp, as ScotCat suggests.
• Timing: after lights-out, when it forages in the wild.
• Portion: what has gone by the morning; remove leftovers.

Watch the belly from the front glass: well fed, it is gently rounded. If it looks hollow, feed later and closer to the fish's cave before adding more food.

Introduce it calmly to a mature aquarium

Add the fish only to a filtered aquarium that has run long enough to process waste, with zero ammonia and nitrite and the temperature already in range. Our pleco care guide covers the general set-up for suckermouth catfish.

OATA recommends acclimatising with the lights off: float the sealed bag for about 10 minutes, add small amounts of aquarium water over up to 20 minutes, and release the fish with as little bag water as possible. Catfish should travel double-bagged because their fin spines can pierce a bag. Our acclimatisation guide covers each step.

Use a first-week checkpoint plan

Hiding for the first days is normal. Rapid breathing or gasping at the surface is not: test the water, increase aeration and check the temperature at once.

Give it calm company and its own territory

Planet Catfish calls the L012 peaceful if a little territorial. For the very similar Ancistomus L163, Seriously Fish recommends a South American set-up with characins, peaceful cichlids and catfish such as Corydoras and other loricariids, and warns that several plecos need a refuge each.

Screen each companion

For plecos with similar care, compare the L134 Leopard Frog Pleco, the L075 Para Pleco, the L103 Pleco and the grey L128 Blue Phantom Pleco, or browse our L-number plecos, the wider South American catfish range, all catfish and plecos and our rare and collector fish. Check a planned mix with our tank mates tool.

Watch for problems early

OATA describes a healthy fish as having clear, bright eyes, undamaged fins, no ulcers or bumps, normal swimming and steady breathing, and lists clamped fins, flicking against décor and shimmying as warning signs. Seriously Fish advises checking newly imported Ancistomus for a rounded belly and eyes that are not sunken, the classic signs that a loricariid is feeding well.

Pair each sign with an action

Test first, then act. Low oxygen and poor water quality cause most problems in rapids plecos, and both are fixed by maintenance rather than medicine.

Breed L012 in caves

Planet Catfish and ScotCat both describe it as a cave spawner, but no breeding report has been published. Adults can be sexed: Planet Catfish says males develop small tooth-like odontodes on the leading pectoral-fin rays and on the back half of the body, while females stay unadorned and are wider across the body, most clearly just behind the pectoral fins when seen from above.

Set up for a spawning

1. Choose a sexed pair by the odontodes and body width described above.
2. Offer adult-sized caves in moving water, more caves than fish.
3. Condition the pair with warm, highly oxygenated water, frequent large water changes and a varied diet.
4. Leave a guarding male alone and avoid moving his cave.
5. Record the details and share them, because no breeding report exists for this species yet.

Answer L012 Gainsboro Pleco buying questions

Which species is the L012 Gainsboro Pleco?

L012 is Ancistomus feldbergae, a suckermouth catfish from the Rio Xingu basin in Pará, Brazil. It was described in 2012 as Peckoltia feldbergae and moved to Ancistomus in 2015. Planet Catfish lists L013 as a young L012.

How do I recognise a true L012?

The original description, summarised by FishBase, gives dark brown dots over the whole body, an orange band on the outer edge of the dorsal and tail fins, and thin dark stripes in the dorsal-fin membranes that break into small dots in larger fish.

How big does Ancistomus feldbergae grow?

FishBase and ScotCat give about 17 cm and Planet Catfish 200 mm standard length. Plan for a pleco of about 17–20 cm without the tail.

What size aquarium does it need?

No minimum is published. Planet Catfish suggests about a 30 cm square of floor, broken up with rocks and wood, for each fish. For comparison Seriously Fish recommends a 120 × 45 cm base for the smaller snowball pleco, a sensible minimum here.

What water conditions does it need?

Warm, clean, oxygen-rich water with a current. Planet Catfish gives 25–30°C and ScotCat 25–29°C with pH 6.0–7.5; ScotCat adds that it needs a high oxygen level. We suggest 26–29°C.

Is it a good algae eater?

Not reliably. Wild fish feed mainly on diatoms scraped from rocks, but Planet Catfish says aquarium fish lean towards meaty foods and are not effective algae eaters. Feed both plant-based and meaty sinking foods.

Is it peaceful?

Yes. Planet Catfish calls it peaceful if a little territorial, so give every fish its own area and cave and avoid crowding several plecos together.

How many fish come with one purchase?

One live fish of the standard size currently available. Sex is not chosen or guaranteed.

Consult the care references

• Planet Catfish: Ancistomus feldbergae (L012) — names, L013 as a young L012, type locality, size, sexing, temperature, feeding, décor and compatibility.
• FishBase: Ancistomus feldbergae — diagnosis, maximum length, wild habitat and stomach contents from the original description.
• ScotCat: Ancistomus feldbergae — synonym, sexing, care, diet, size, water values and a summary of the IUCN Least Concern assessment.
• Seriously Fish: Ancistomus sp. L163 (Big Spot Peckoltia) — the similar L163, its confusion with L013, stream-style set-up and community advice for Ancistomus.
• Armbruster, Werneke & Tan (2015), review of Hemiancistrus, Peckoltia and allied genera, ZooKeys 480: 97–123 — peer-reviewed review recognising Ancistomus as a valid genus for A. snethlageae and A. feldbergae.
• Seriously Fish: Hypancistrus inspector (L102) — the closest relative, the snowball pleco: aquarium base, hardness, maintenance and filtration guidance used here as a comparison.
• OATA: How to look after freshwater catfish — UK group-level catfish guidance on water quality, substrate, bagging, handling, introduction and maintenance.
• OATA: How to test water quality in your freshwater aquarium — UK guidance on water testing, conditioners and weekly water changes.
• Tropical Fish Co delivery policy — current dispatch days and Live Arrival Guarantee terms.