L330 Watermelon Pleco (Panaque nigrolineatus laurafabianae)

Choose an L330 Watermelon Pleco for a large, wood-filled aquarium

The L330 Watermelon Pleco is the spotted royal pleco of the Guaviare River basin in Colombia, at the south-western corner of the Orinoco system. Royal plecos, Panaque nigrolineatus, are normally boldly striped. Fish from the Guaviare are usually boldly spotted instead, which earned them the trade name watermelon pleco. In 2020 Armando Ortega-Lara and Nathan Lujan described this population as the subspecies Panaque nigrolineatus laurafabianae, named after Ortega-Lara's daughter, Laura Fabiana. You will also see it sold as the Royal Panaque Spotted, the spotted royal pleco and L027a.

The describers found the Guaviare fish distinct in range, colour pattern and body proportions, but the genetic differences were very small: under 0.5% divergence in the mitochondrial markers they examined. They therefore named it a subspecies rather than a full species, and Eschmeyer's Catalog of Fishes still lists it as a synonym of P. nigrolineatus. For a keeper the practical point is simple. An L330 needs royal pleco care, planned for a heavy-bodied, wood-eating catfish that grows to around 40 cm.

Check the features that identify a Panaque

The gallery images are representative, prepared from a reference photograph, and do not show the exact fish supplied. Spot size and density vary between individuals, and the pattern changes as the fish matures.

Select one fish and plan for the adult from day one

One purchase quantity supplies one live L330 Watermelon Pleco in the standard size offered. Sex is not specified: the yellow fin edges that mark males appear only in sub-adult fish, so a young L330 cannot be sexed by eye. The fish you receive will be far smaller than an adult, and OATA warns that an off-the-shelf aquarium is unlikely to be big enough for the larger plecos in the long term.

Buy for the adult, not for the juvenile. A young L330 fits easily into a modest aquarium, but over its life it needs the space, filtration and wood supply of a 40 cm fish.

Confirm four things before you order

1. Space: an aquarium at least 180 cm long, or a firm plan to provide one before the fish outgrows its first tank.
2. Wood: several large pieces of real bogwood, enough to feed on and to hide under.
3. Filtration: filters rated well above the tank volume, with mechanical media you can rinse every week.
4. Time: a large water change and a thorough siphon every week, which a wood-eater's waste makes non-negotiable.

Measure first, then order. Arrival times and packing details are on our delivery page.

Plan the aquarium around a 40 cm adult

Planet Catfish gives a maximum of 430 mm standard length for the watermelon pleco, and Scotcat gives 40 cm. FishBase records 43 cm standard length for P. nigrolineatus as a whole. Standard length is measured without the tail, so an adult is longer still from snout to tail tip. All three sources agree that this is one of the large plecos.

For tank size the sources differ. Scotcat recommends an aquarium of at least 180 cm (6 ft) for a single individual, while FishBase gives a minimum of 120 cm for the species. We follow the larger figure, because a 40 cm wood-eater needs room to turn, a territory of its own and enough water to dilute its waste. OATA notes that the very large aquarium fish it calls tankbusters, which include the larger plecos, often need aquariums of more than 500 litres. As an example, a tank measuring 180 × 60 × 60 cm holds about 648 litres before decor; our tank volume calculator works out the figure for your own measurements.

Use a three-step space check

1. Measure the base: at least 180 cm long, with enough front-to-back depth for a 40 cm fish to turn comfortably.
2. Count adult bodies: add the L330 at its adult size to every other fish at its adult size, not at the size you buy.
3. Check the stand and floor: a tank of that size, filled with water, wood and rock, weighs well over half a tonne.

If your aquarium cannot reach that size, choose a smaller species from our L-number plecos instead.

Build a tangle of wood with secure rockwork

Planet Catfish describes the natural habitat of the watermelon pleco as fallen trees and wood tangles. For the royal pleco it calls bogwood essential, both as food and as the fish's preferred hiding place. Build the layout around several large pieces of real aquarium wood, arranged so that the pleco can wedge itself into a dark gap or rest under an overhang during the day.

Large royal plecos rearrange the aquarium to their own liking, and Planet Catfish warns that rocks must be secured so they cannot topple against the glass. OATA gives the same advice for big fish: fix ornaments and rocks firmly and protect heaters from damage. Use sand or fine gravel without sharp edges, which OATA recommends for catfish to protect their sensitive barbels. Where fish may eat or uproot live plants, OATA suggests artificial plants and ornaments instead, so in an L330 tank treat plants as optional.

Divide the footprint by function

Replace wood as it wears down. A royal pleco slowly rasps its wood away, and a piece too small to hide under no longer does its job. Browse our Panaque plecos to compare the other wood-eaters that need the same kind of layout.

Set water values where the sources agree

The three sources give slightly different ranges. The target column uses the band where they overlap, which suits the fish whichever figure you trust.

UK tap water ranges from very soft to very hard depending on where you live, and your water company publishes hardness and pH figures for your postcode. If your supply is harder than about 15 dGH, blending it with reverse-osmosis water is the usual way to bring it into range; make any change gradually and keep it steady from one water change to the next. Our water matcher compares your tap water with this fish, our water chemistry guide explains each reading, and our guide to pH in tropical aquariums covers how to adjust it safely.

Separate habitat values from waste readings

These waste limits come from OATA's catfish care sheet. A tank can sit inside the right temperature and pH and still be unsafe if ammonia or nitrite are present, so test both kinds of reading every week, and again after any change in feeding or stocking.

Filter for a wood-eater's waste

Scotcat links this pleco's need for plenty of water changes and powerful filtration directly to its wood-eating habits. A Panaque spends much of its time rasping wood, and much of what it scrapes off passes through as fine, fibrous waste that settles on the sand and clogs filter sponges. For very large fish, OATA advises several large aquarium filters, or even a pond filter, to cope with the volume of solid waste. Our guide to aquarium filtration explains how mechanical and biological filtration share that work.

Follow a weekly maintenance sequence

1. Test ammonia, nitrite and nitrate before you start.
2. Siphon the fine wood waste from the open sand and from under the wood, where it collects.
3. Change at least 25% of the water, the weekly minimum OATA recommends; a larger change suits a tank holding a big wood-eater.
4. Treat new water with a conditioner that removes chlorine and chloramine, and match its temperature to the tank.
5. Rinse mechanical media in the removed tank water, never under the tap, and leave most of the biological media undisturbed.

If ammonia or nitrite ever read above zero, reduce feeding, change water and find the cause before adding more fish.

Feed wood, vegetables and sinking foods

Planet Catfish describes the classic pleco diet of greens: royal plecos can be weaned onto most vegetables, with tinned peas a favourite, and they eat bogwood. Scotcat adds cucumber, courgette and sinking tablets, and stresses that wood must be part of the set-up. Some prepared foods should supplement the vegetables. OATA advises buying organic vegetables or washing them thoroughly, because residual pesticides can harm fish.

New royal plecos can be fussy feeders. Planet Catfish advises waiting until the fish is feeding well before adding large, boisterous tank mates that might take its food.

Build one measured meal

• Wood, always: keep enough bogwood in the tank that the fish can rasp it at any time.
• Vegetables in the evening: a slice of courgette or cucumber, or a few peas, weighted down near the wood shortly before the lights go out.
• Sinking food: a few plant-based sinking tablets or wafers, adjusted so none are left by morning.
• Remove leftovers: lift uneaten vegetables the next morning so they do not foul the water.
• Check the belly: a well-fed pleco has a gently rounded belly; a hollow belly means it is not getting enough.

Introduce the pleco to a mature aquarium

Add an L330 only to a biologically mature aquarium with zero ammonia and nitrite, water at 24–26°C and pH 6.5–7.5, and the wood already in place. Catfish have sharp fin spines, and OATA recommends double bagging them for that reason, so open the bag with care.

Use the floating bag method OATA describes: switch off the aquarium lights, float the bag for about 10 minutes to equalise the temperature, then add small amounts of tank water to the bag over up to 20 minutes. Release the fish with as little bag water as possible. Our guide to acclimatising new fish covers each step. Guide the pleco out of the bag into a container rather than lifting it in a net, because its spines and rough skin snag easily in netting.

Use a first-week checkpoint plan

Watch the pleco and act on changes

Planet Catfish describes the royal pleco as very secretive, so daily checks need a little patience: look into its wood and caves rather than expecting it out in the open. OATA lists the general warning signs for catfish: hanging at the surface, sitting on the bottom or swimming erratically, turning darker or paler, hiding more or becoming more aggressive, breathing faster or slower than normal, white spots or fluffy growths, lost fins or scales, a change in body condition and reduced interest in food.

Pair each observation with an action

Record your readings and any changes before treating anything, and contact us with them if a problem continues.

Choose tank mates for a territorial wood-dweller

Planet Catfish describes the watermelon pleco as generally peaceful but ready to defend its territory against its own kind. For the royal pleco it adds that it is territorial with other similarly sized catfish and otherwise peaceful with smaller fish. Because the pleco is so secretive, Planet Catfish suggests livelier fish to give the aquarium movement during the day.

Decide from the suits and avoid list

In an aquarium of the size this pleco needs, good companions from our range include the Tinfoil Barb and the Spotted Red-Cheek Silver Dollar for movement in the upper water, and the Giant Danio for a fast-swimming school. Check any mix with our tank mates tool before you buy.

To compare related plecos, see our L027 Royal Pleco, the striped Royal Pleco (Panaque nigrolineatus), the L190 Golden Royal Pleco and the L090 Papa Panaque, or browse all our catfish and plecos, South American catfish and centrepiece fish. Our pleco care guide covers the basics every pleco shares.

Know the limits of breeding and supply

Planet Catfish lists breeding of the watermelon pleco as unreported in the aquarium, so the fish in the trade are collected from the wild. Ortega-Lara and Lujan note that the spotted Guaviare population is heavily exploited for export because of its popularity, which is a good reason to buy one only when you can give it a home for life. FishBase lists P. nigrolineatus as Least Concern on the IUCN Red List (assessed 2020); the subspecies itself has not been evaluated.

Answer L330 Watermelon Pleco buying questions

What is an L330 Watermelon Pleco?

It is the boldly spotted royal pleco from the Guaviare River basin in Colombia. Ortega-Lara and Lujan described it in 2020 as the subspecies Panaque nigrolineatus laurafabianae, although some catalogues still treat it simply as P. nigrolineatus. It is also sold as the Royal Panaque Spotted and as L027a.

How big does an L330 get?

Planet Catfish gives 430 mm standard length and Scotcat gives 40 cm, both measured without the tail. Plan for a heavy-bodied catfish of around 40 cm or more.

What size aquarium does it need?

Scotcat recommends at least 180 cm (6 ft) for a single fish. FishBase gives a 120 cm minimum for the species, but for a 40 cm adult we follow the larger figure.

Does it really eat wood?

Yes. Panaque are wood-eating plecos, and both Planet Catfish and Scotcat say real bogwood must be in the aquarium. The wood is part of its diet as well as its hiding place, so add vegetables and sinking foods alongside it.

Will my L330 keep its spots?

Planet Catfish says the spotted pattern stays fairly constant from juvenile to sub-adult, but fully grown fish become more or less striped, sometimes keeping a few spots.

Can I keep two L330s together?

Only in a very large aquarium with separate wood and hiding places for each. They are generally peaceful but defend their territory against their own kind and other similarly sized catfish.

What water does it need?

Aim for 24–26°C and pH 6.5–7.5, the range where Planet Catfish, Scotcat and FishBase overlap. Keep ammonia and nitrite at zero and nitrate no more than 20 mg/l above your tap water.

Will it clean algae from my tank?

Not reliably. It is mainly a wood and vegetable eater and produces a lot of waste. OATA points out that no algae-eating fish is a substitute for regular maintenance.

Consult the care references

• Planet Catfish: Panaque nigrolineatus laurafabianae (L330): size, identification, pattern change, sexing, range, habitat, diet and compatibility.
• Planet Catfish: Panaque nigrolineatus: royal pleco water values, wood, rockwork, feeding and tank mates.
• Scotcat: Panaque nigrolineatus laurafabianae: the 2020 description, aquarium length, water values and diet.
• FishBase: Panaque nigrolineatus: recorded size, water values, aquarium minimum and IUCN status.
• OATA: How to look after freshwater catfish: UK guidance on water quality, acclimatisation, maintenance and health signs.
• OATA: How to look after very large fish / tankbusters: aquarium size, filtration and secure decor for large fish.
• OATA: How to look after tropical algae eaters: washing vegetables and why algae eaters do not replace maintenance.