L034 Ancistrus ranunculus

Decide whether this specialist pleco suits you

The L034 pleco (Ancistrus ranunculus) is a freshwater, bottom-living loricariid from the Xingu and Tocantins river basins of Brazil that reaches 19.5 cm. It suits experienced keepers prepared to provide warm, highly oxygenated water, sustained movement, secure rock refuges and deliberate feeding. Its generally peaceful nature does not make it a routine community choice because the aquarium must be planned around these specialised conditions.

Understand its natural behaviour

FishBase places Ancistrus ranunculus in the Xingu and Tocantins river basins of Brazil. It inhabits clear running water and uses narrow cracks, passages between overlapping rocks and spaces beneath flat rocks. During the dry season it has been recorded at depths of up to 3 metres in water without a strong current. These observations explain why close-fitting rock refuges matter, while aquarium husbandry still calls for substantial movement and oxygenation.

The same reference records a maximum of 19.5 cm total length for a male or unsexed fish and classifies the wild population as Near Threatened. Plan conservatively around that recorded maximum rather than treating a dispatch measurement as the final size.

Choose it for the right reason

This is not simply an algae-control purchase. Its species diet is more protein-rich than that of many other Ancistrus, and it still needs deliberate feeding. It also requires a refuge of its own and tank mates able to thrive in the same warm, moving water. Browse the bristlenose pleco collection if you want to compare that commitment with other members of the group.

Plan space, water and adult size together

Seriously Fish gives an 80 × 30 cm aquarium base, equivalent to about 72 litres, as sufficient for a couple of specimens. Larger quarters are required for a group. Use the footprint as the decisive measurement because this bottom-dwelling fish needs usable floor area for rocks, passages and separate refuges, not just water above it.

Plan around FishBase’s recorded maximum of 19.5 cm total length. Seriously Fish separately records 13 cm standard length. Lay out each shelter and passage for a fish approaching the larger 19.5 cm planning figure.

Use these planning values

The aquarium profile gives 25–30°C, while FishBase records 25–28°C for the species’ wild environment. A routine target of 25–28°C remains inside both ranges. Keep pH between 6.0 and 7.0 and hardness between 2 and 10 dGH.

These requirements work as one system. Warm water must remain well oxygenated, the filter must process the fish’s waste, and the arrangement must preserve enough floor space for secure retreats. A nominally large aquarium is still a poor fit if rockwork occupies every passage or the filter cannot create the required movement.

Choose the dispatch size without confusing adult size

One purchase supplies one animal of the size selected on the live selector. The size choices are labelled 4–6 cm, 5–7 cm and 8–9 cm; use the selector to see which choice can be ordered. The size you select is the size supplied, not the adult size.

A smaller dispatch measurement does not establish age, sex or eventual length. Prepare the same adult aquarium before ordering any of the size choices, with an 80 × 30 cm base, suitable water movement and a refuge laid out for the larger planning size. This avoids making a temporary measurement responsible for a long-term space decision.

Read the offer literally

• Quantity: one purchase means one animal, even when a gallery scene shows two fish.
• Size: the chosen label describes dispatch size.
• Adult planning: allow for the recorded maximum of 19.5 cm total length.
• Group planning: select the required purchase quantity separately and provide one refuge per fish.

Sex is guaranteed only when the selected option explicitly states male or female. This L034 Ancistrus ranunculus listing has no sex-guaranteed option.

The gallery images are representative, based on reference photographs of this species, so colours can look slightly different from the live animal.

Build secure rock passages and refuges

Start with an aquarium base of at least 80 × 30 cm, equivalent to about 72 litres. That footprint is described as sufficient for a couple, while a group needs larger quarters. For a single fish, the same baseline leaves room for the filter, current and adult-sized refuge without forcing every function into one small area.

Shape the bottom around natural shelter choices

Use aquarium sand or gravel with rounded stones and rocks. Create narrow passages between securely positioned rocks and shaded spaces beneath flat pieces, reflecting the places this fish uses in the Xingu and Tocantins systems. Every structure must remain stable when the fish moves beneath or alongside it.

Give each specimen a refuge it can occupy without sharing an entrance. The opening should admit the fish comfortably while still feeling enclosed. If two fish repeatedly meet at the same shelter, add or reposition cover rather than expecting them to divide one preferred crack peacefully.

Preserve movement around the structures

• Leave a clear route for water to travel across the aquarium.
• Keep filter intakes and outlets clear of unstable stones and trapped debris.
• Provide more than one route around major pieces of rock.
• Check that a growing fish will not become confined by a passage designed around its dispatch size.

A stream-style arrangement suits the species, but a planted aquarium can also work. High movement may make some live plants difficult to maintain, so prioritise oxygenation and fish access over a dense planting plan. Plants must not block the outlet, close a refuge entrance or remove the open base needed for movement.

Inspect the layout from the fish’s level before filling the aquarium. A cave that looks spacious from above may taper sharply at the rear, while stacked rocks can create an inaccessible trap. Build for a fish approaching 19.5 cm total length and leave enough room for it to turn or reverse out.

Hold water inside the species ranges

Set the routine temperature to 25–28°C. This target remains within both the 25–30°C aquarium range and FishBase’s 25–28°C environmental record. Maintain pH 6.0–7.0 and general hardness 2–10 dGH. Stability within those limits is more useful than repeatedly moving a reading towards an arbitrary midpoint.

Measure before you adjust

Test the aquarium rather than estimating from the local water supply or an earlier result. Our water chemistry guide explains what the principal readings mean, while the water matcher lets you compare measured values with this fish’s target range.

Temperature, pH and hardness must also suit every proposed tank mate. A fish described as peaceful is not compatible if it needs cooler, harder or more alkaline water. Screen the shared range before temperament or colour.

Place the thermometer where it represents the occupied aquarium rather than directly beside the heater. Test after equipment changes and continue weekly water-quality checks, because a correct temperature does not reveal ammonia, nitrite or nitrate.

Combine strong filtration with weekly testing

This species needs well-oxygenated water with substantial movement and will not do well without a degree of current. For an aquarium of about 72 litres, the species profile recommends turnover of four to five times the volume each hour. That calculation gives 288–360 litres per hour, aligning with its suggested filter rating of about 290–360 lph.

Calculate from the real aquarium

Multiply the aquarium volume by four and five to create the starting turnover band. A 72-litre aquarium gives 288–360 lph; a different volume needs its own calculation. Filter ratings are a selection aid, while rocks, media condition and outlet position influence how movement reaches the occupied part of the aquarium.

The RSPCA explains that a working biological filter supports bacteria that convert toxic ammonia to nitrite and then to the safer nitrate. Keep that filter running and maintained; water movement alone does not replace biological filtration.

Use measurable waste limits

OATA’s freshwater algae-eater sheet gives group guidance: test water weekly, hold ammonia and nitrite at 0 mg/L, and keep nitrate from exceeding 20 mg/L. It also stresses that algae-eating fish are not substitutes for maintenance or appropriate stocking.

At least once a week, change 25% of the aquarium water. If waste readings rise, check feeding, stocking, trapped food and filter performance together. Correct the cause rather than relying on an algae-eating fish to disguise it. Keep enough surface movement to support oxygenation without allowing unstable rockwork to shift.

Feed a protein-rich Ancistrus diet

Ancistrus ranunculus prefers a more protein-rich diet than most Ancistrus. Use a quality sinking dried food as the regular base and add live or frozen foods such as bloodworm, chopped mussel or prawn. Do not treat algae growth, wood or general aquarium debris as a complete diet.

Build a measured feeding routine

Start with a modest portion that reaches the fish and remove anything left uneaten before it breaks down. Bottom-feeding fish may need time to locate food, so watch whether the portion is actually reached rather than increasing it automatically. Uneaten food adds toxic waste to the aquarium.

Place the food where the fish can reach it without entering another specimen’s refuge. In a multi-fish aquarium, use separated feeding positions and watch each position rather than assuming one missing portion means every fish ate. Territorial bickering around shelter can also restrict access to food.

Respond to what you observe

• If food remains, reduce the next portion and remove the waste.
• If another fish takes the entire portion, separate feeding locations before adding more food.
• If algae persists, review maintenance and water chemistry rather than increasing the pleco’s stocking level.
• If the fish repeatedly misses food, check refuge access, competition and the placement of sinking food.

A rounded belly and eyes that are not sunken are useful condition checks for loricariids. Feeding success should therefore be judged by both food uptake and body condition, not by whether the aquarium glass looks cleaner.

Size the heater and flow for the real room

Choose equipment for the aquarium volume, room temperature and rock layout rather than copying a wattage or flow rate without context. For a roughly 72-litre aquarium in a room around 20°C, the species profile estimates about 125–150 W to hold 25–30°C. Because the routine target here is 25–28°C, treat that wattage as a contextual equipment example and confirm stable operation with a thermometer.

Separate three equipment jobs

• Heater: holds the routine 25–28°C range.
• Biological filter: processes ammonia and nitrite.
• Outlet or additional circulation: creates movement and supports oxygenation across the occupied base.

One device may contribute to more than one job, but do not assume a visible current proves that biological filtration is mature. Likewise, a filter can process waste while leaving sheltered corners with little movement. Check the whole route from outlet to intake after rocks and refuges are in place.

Make a worked flow check

For 72 litres, four times turnover is 288 lph and five times is 360 lph. Start by looking in the 290–360 lph rating range, then assess how the completed arrangement distributes that movement. If plants bend or fail under the required current, simplify the planting rather than reducing oxygenation below the fish’s needs.

Secure cables and equipment so maintenance does not disturb the rockwork. Keep the heater exposed to circulating water and leave the filter intake accessible for inspection. A hidden intake that cannot be checked encourages debris accumulation, while an outlet blocked by plants or stone cannot distribute movement effectively.

Prepare the aquarium before arrival

Have the aquarium fully prepared before the fish arrives. The biological filter must be established, the heater must hold 25–28°C, and tests must show 0 mg/L ammonia, 0 mg/L nitrite, pH 6.0–7.0 and hardness 2–10 dGH. Complete the rockwork and confirm that every refuge remains stable before adding livestock.

If this is your first setup, use our guide to preparing and maturing a tropical aquarium before choosing a delivery date. Maturation applies to the biological filter and aquarium system, not to a container of water.

Complete a pre-arrival check

1. Run the heater and confirm 25–28°C with a thermometer.
2. Test ammonia, nitrite, nitrate, pH and general hardness.
3. Confirm sustained movement across the lower part of the aquarium.
4. Check that the refuge is accessible to an adult-sized fish.
5. Ensure tank mates have already passed the water, current and space screen.
6. Arrange for someone to receive the live-animal parcel.

Test the completed layout as a system

Run the aquarium with the rocks, substrate and refuges in their final positions before arrival. Watch whether movement reaches the spaces beside and beneath the cover rather than travelling only across the surface. Check the outlet after any stone or plant is moved, because a small change can redirect flow away from the occupied base.

Use the same completed arrangement when checking temperature and water quality. A reading taken before the heater, filter and rockwork settle into normal operation may not represent the conditions the fish will occupy. Confirm that the filter intake remains accessible, that debris is not collecting behind a refuge and that every rock stays secure during routine maintenance.

Follow the store acclimatisation steps

Read the current delivery and Live Arrival Guarantee policy before the delivery window.

1. Have someone present to receive the parcel because live fish cannot be left unattended.
2. Start filming before opening the parcel, with the parcel still sealed and the outer box visible.
3. Open the parcel in one continuous take.
4. Keep filming with the fish still inside the sealed bag so its condition is visible before anything is disturbed.
5. Float the bag for 20–30 minutes.
6. Release the fish without pouring the bag water into the aquarium.

Keep the prepared refuge clear during release so the fish can move directly into cover. Do not dismantle the rockwork to make the animal remain visible. Once released, restore the aquarium to its normal calm routine and observe without repeated disturbance.

Use condition and water readings as checkpoints

Judge progress through visible condition, food uptake and measured water quality. A healthy-looking loricariid should have a rounded belly rather than a hollow profile, and its eyes should not appear sunken. These checks are especially important for a species described as difficult to maintain when it arrives in poor condition.

Check during the first week

• Feeding: confirm that sinking food reaches the fish and is eaten.
• Body condition: watch the belly and eyes without repeatedly disturbing the refuge.
• Shelter access: make sure another bottom-dweller is not controlling the entrance.
• Flow: confirm that the outlet still creates movement around the occupied base.
• Waste: remove uneaten food before it breaks down.

If the fish misses food, first check competition and placement. If its belly becomes hollow, its eyes appear sunken or another health change develops, contact us with the aquarium readings and a clear description of the change.

Establish the first-month rhythm

Continue the measured feeding routine and weekly water testing. Record ammonia, nitrite, nitrate, temperature, pH and hardness so a change can be seen rather than guessed. Recheck filter movement after cleaning or repositioning equipment, because a shifted outlet can alter oxygenation around the refuges.

Expect some territorial bickering when more than one specimen is kept. If repeated disputes centre on one shelter, provide a separate refuge and more usable floor space. Do not solve a shelter conflict by adding food throughout the aquarium; extra food raises the waste load without creating another territory.

Handle with particular care

Cheek odontodes and pectoral spines can become entangled in a net. Avoid unnecessary capture. When movement is essential, prepare the destination first and minimise the time spent pursuing or restraining the fish.

Screen tank mates for specialised conditions

Ancistrus ranunculus is generally peaceful, but it is not an automatic match for a general community aquarium. Compatibility begins with its specialised environment: 25–28°C, pH 6.0–7.0, hardness 2–10 dGH, high oxygenation and substantial movement.

Apply the water-and-space screen first

• The proposed fish must remain comfortable throughout 25–28°C.
• Its pH and hardness needs must overlap 6.0–7.0 and 2–10 dGH.
• It must tolerate sustained movement and well-oxygenated water.
• It must not prevent this pleco from reaching food or its refuge.
• The combined adult sizes must fit the aquarium base and filtration capacity.

In a biotope-style arrangement, Seriously Fish identifies Anostomus, Hemiodus, Semaprochilodus and Metynnis species, reophilic Retroculus cichlids and other loricariids requiring similar conditions as possible companions. These are conditional examples, not universal pairings. Adult size, behaviour, group requirements and the exact water range still need checking for the proposed species.

Protect access to the bottom

Map where every bottom-dweller will shelter and feed. Two fish described as peaceful may still compete if both depend on the same crack, cave or sinking-food position. Add separate refuges and separated feeding points before adding another bottom-oriented fish.

There is honest uncertainty whenever individual temperament, aquarium layout and an exact mix of fish have not been observed together. For a stocking and compatibility assessment, contact us with the aquarium dimensions, measured water values, filtration, established livestock and intended purchase quantity.

Give each specimen its own refuge

A single specimen avoids competition with another Ancistrus ranunculus for the same preferred crack. More than one can be kept when space and shelter are planned properly: about 72 litres with an 80 × 30 cm base is described as sufficient for a couple, while a group requires larger quarters.

Translate quantity into floor-space decisions

A “couple” in the aquarium-size guidance means two specimens; it does not make them a sexed or breeding pair. Choose quantity for the space you can provide and expect territorial bickering when multiple fish establish preferred shelters.

Refuges should be genuinely separate rather than two entrances into the same contested hollow. Spread them across the footprint while keeping the rockwork secure. Place sinking food so one fish cannot control every feeding point from a single shelter.

Check whether the layout works for every fish

Observe access rather than counting caves alone. A refuge is useful only when its entrance, surrounding floor and approach route remain open to the intended fish. If one specimen stays outside while another moves repeatedly between several shelters, redistribute the cover so each fish has a practical retreat.

Check feeding access at the same time. Separated food positions should allow each specimen to reach sinking food without crossing the entrance controlled by another fish. When one fish consistently misses food, change the positions and shelter arrangement before increasing the amount offered.

As the fish grow, repeat the space check using their larger bodies rather than the dispatch measurements. A route that once allowed two specimens to pass may become a point of conflict, and an entrance can become too narrow. Enlarge the usable layout while keeping all rockwork stable and preserving movement around the bottom.

Reassess when behaviour changes

If disputes remain brief and every fish retains access to shelter and food, continue monitoring. If one fish is repeatedly displaced, redesign the shelter distribution or increase usable space. The solution is more appropriate territory, not reliance on the species’ generally peaceful description.

Answer the main buyer questions

How big does L034 Ancistrus ranunculus get?

L034 Ancistrus ranunculus reaches a recorded maximum of 19.5 cm total length. Plan every refuge and passage around that adult figure rather than its dispatch size.

What size aquarium does L034 Ancistrus ranunculus need?

Start with an 80 × 30 cm base, equivalent to about 72 litres. Seriously Fish describes that footprint as sufficient for a couple, while a group requires larger quarters.

How many L034 Ancistrus ranunculus should I keep together?

You can keep one fish or plan about 72 litres with an 80 × 30 cm base for a couple. Give each fish its own refuge and use larger quarters for a group.

Does L034 Ancistrus ranunculus suit beginners?

L034 Ancistrus ranunculus is better suited to an experienced keeper because it needs warm, highly oxygenated water, substantial movement, secure refuges and careful feeding.

What does L034 Ancistrus ranunculus eat?

Feed L034 Ancistrus ranunculus a quality sinking dried food with regular live or frozen bloodworm, chopped mussel or prawn. Remove uneaten food before it breaks down.

What temperature and pH does this fish need?

Keep it at 25–28°C and pH 6.0–7.0, with general hardness of 2–10 dGH. The temperature is the overlap of FishBase’s 25–28°C environmental record and Seriously Fish’s 25–30°C aquarium range.

Is it aggressive or likely to nip fins?

This fish is generally peaceful, but multiple specimens may show territorial bickering around refuges. Give each fish its own shelter and monitor whether every specimen can reach food and cover.

Which kinds of animals can live with it?

Possible companions include Anostomus, Hemiodus, Semaprochilodus or Metynnis species, reophilic Retroculus cichlids and other loricariids requiring similar conditions. Check that the exact species shares 25–28°C, pH 6.0–7.0, 2–10 dGH, strong movement and high oxygenation.

How does this fish arrive alive?

Start filming every delivery with the parcel still sealed, then open it in one continuous take and show the fish still inside the sealed bag. Someone must be present to receive it; float the bag for 20–30 minutes, then release the fish without pouring the bag water into the aquarium.

Check the underlying references

• FishBase: Ancistrus ranunculus — scientific identity, family, distribution, environment, recorded maximum length and conservation classification.
• Seriously Fish: Ancistrus ranunculus — aquarium footprint, water ranges, flow, diet, behaviour, refuges and handling considerations.
• OATA: Tropical algae eaters — UK group guidance on feeding, testing, waste limits, filtration and aquarium preparation.
• RSPCA aquarium environment guidance — biological filtration and the processing of ammonia, nitrite and nitrate.
• Tropical Fish Co delivery and Live Arrival Guarantee policy — receipt, filming, floating time and bag-water instructions.