Gold Nugget Plecos: Treasure from the Xingu

Oliver Lucanus

When photos of the Xingu plecos first appeared in the aquarium literature in the early 1990s, it changed the landscape of the hobby. Catfishes, until then, had been used to clean the aquarium, but they suddenly became the center of attention, and today thousands of aquariums are set up just to keep the fish once referred to as “suckerfish” and “algae cleaners.”
 
While the zebra pleco (Hypancistrus zebra, L046) and the scarlet cactus pleco (Pseudacanthicus pirarara, L025) stole most of the spotlight, and still do today, the introduction of the gold nugget pleco still caused a stir. But because of its comparatively low price and wide availability, it is one of the more misunderstood species and is often kept in unsuitable conditions. Let us have a look at the basic factors important to keeping this beautiful fish in the aquarium.
 

Natural History

The gold nugget pleco is a highly variable species, found from the lowland region of the Xingu at Belo Monte, upstream to above São Félix do Xingu. This variability led to many L-numbers being issued for the same species—L018, L081, L085, L177, and LDA060. But today this fish has a proper scientific name, Baryancistrus xanthellus, which is valid for the lowland variant, devoid of any yellow spots, as well as the yellow-spotted variants found upstream in the Xingu and Iriri rivers. 
 
As adults, the bright yellow margins on the dorsal and caudal fin begin to disappear and the spot pattern becomes finer and less conspicuous. The coloration of the juvenile gold nuggets for sale in stores has actually little effect on their adult pattern once they reach their adult size of about 9 inches (23 cm).
 
This is one major misconception about this beautiful loricariid catfish: It gets much larger than the small fish you find in the aquarium shop. Adult specimens rarely get exported because they need much more water for transport and simply become too expensive for resale. A large aquarium of at least 100 gallons (at least 380 liters) is certainly needed to properly house a group of adult gold nuggets. 
 
Gold nugget plecos live in the warm, shallow waters of the Xingu and Iriri rivers, in the strongest water flow of the rapids. These somewhat rigid requirements brought about by their natural habitat also make them less than ideal community aquarium fish and actually much more difficult to keep than many of the other colorful plecos. It is vital that their water is warm—around 86°F (30°C)—and well oxygenated. For their powerful suckermouths, no amount of current is too much; the current where they occur in nature is often so strong that it is impossible for a snorkeler to hold on in it.
 
The Xingu’s clear, shallow water flows over rocky substrates covered in algae and biofilm that is the main food source of the gold nuggets. Even adults can be seen throughout the day scraping the biofilm off the rocks, like a herd of buffalo grazing on prairie grass. These are the most commonly seen catfish in the Xingu basin and, therefore, the most commonly exported fish from the Xingu.
 

Collecting Gold Nuggets

Unlike for many of the other plecos there, dive gear is not needed to procure gold nuggets. They can be collected by skilled fishermen in knee- or hip-deep water in the rapids. While not easy, it is comparatively cheap and efficient. The fishermen, equipped with round, weighted nets around 24 inches (60 cm) in diameter, snorkel the rapids, looking for the plecos that rush to hide under the nearest boulder at any noise or shadow from the approaching humans. 
 
Once a pleco has been located, a net is draped over the boulder and the fish is scared into it by hand. Catfish are kept in soda bottles tied to fishermen’s belts until several are collected and returned to the boat. There the fish are held in shallow trays, often for several days until the boat returns to the city, where the trays are kept on racks with the addition of a simple air stone and frequent water changes. 
 
To the people living along the river, catching fish for the aquarium industry is one of few possible sources of income. Alternatives such as gold mining or working on an industrial agriculture or cattle farm all have a much greater impact on the environment. 
 
The gigantic Belo Monte dam project, farming, deforestation, and gold mining all pose greater threats and will eventually destroy the Xingu river. By comparison, the legal collection of aquarium fish is very much sustainable, because gasoline prices dictate how far the fishermen go to obtain the river’s most common pleco. This stands in stark contrast to collection of the zebra pleco, whose illegal overfishing by traffickers is further threatening the survival of the species. 
 
Like many habitats of our most favorite aquarium fish, the Xingu faces unprecedented threats that have already greatly affected the river and will continue to do so. The Belo Monte dam removes much of the vital flow to the Volta Grande, the most diverse section of the lower Xingu. The absence of the seasonal dynamic will eventually cause species to disappear, and habitat has already been lost forever. 
 
Upstream, the upper Xingu has already been completely deforested by industrial agriculture and cattle farms, while small tributaries are laid to waste by gold miners, who release mercury into the river basin. Only the areas falling into native Indian lands and national parks are currently somewhat protected, but even those are under severe threat from legislation introduced by Brazil’s current administration.
 
Added to all of that is the increased threat of climate change and increased drought that has affected the region. It is shocking to think that Brazil’s most beautiful and diverse river may eventually fall victim to the never-ending destruction of the Amazon.
 

Aquarium Care

Once the gold nugget plecos are shipped, they arrive after nearly 40 hours of travel in North America or Europe. Packed individually with 40 to 60 per box, they are often stressed and need time to acclimate to their new environment. Before buying any, wait at least one week to select your fish to make sure they have adapted well after the shipping stress. To select a healthy specimen, look for three basic signs:
 
·       Clear eyes that are not sunken into the eye sockets, indicating overall good health
·       A slightly rounded stomach, indicating that the fish is eating
·       Pectoral and ventral fins that lie flat, hugging the substrate and not standing up at odd angles, indicating that the gills are parasite free and the fish does not suffer from oxygen stress 
 
The stress these fish are subject to is why the gold nugget pleco is regarded as somewhat of a problem species that is rarely bred and not often successfully kept long term. Knowing how they are collected and about their wild lives can help us to better understand how to maintain them in the aquarium.
 
Gold nuggets are not community fish; they require too much food and too high of a water quality to do well in a normal aquarium with a wide variety of fish. In the rather sterile conditions of the average aquarium, there is just not enough food for them, so their diet must be supplemented with zucchini, sweet potato, green-based prepared foods, and sinking tablets. Care must be taken to avoid overfeeding, which will pollute the water; gold nuggets do not tolerate poor water conditions. 
 
While they are often found in fast-flowing water with a very strong current, this is not needed to reproduce in the aquarium. The gold nugget will greatly appreciate high aquarium water current, but provided the water is well oxygenated, it need not be torrential. This fish is intolerant of built-up organic wastes in the water, so the tank must be well filtered. Frequent large water changes are another must to maintain excellent water quality. 
 
Complicating this is the need for warm water. Gold nuggets appreciate water on the higher end of the tropical fish spectrum, in the upper 80s (25-30°C), which can lower the availability of oxygen, particularly if the water quality is sub-optimum. Maintaining these parameters in balance is a challenge for the aquarist. 
 
Choosing tankmates can become a similar challenge. While there are certainly other rheophilic periphyton-grazing fish available, tankmates that compete for similar food sources should be avoided at all costs. 
 
Several tetras are available from the region, including the beautiful giant golden dawn tetra (Moenkhausia heikoi). The small cichlids of the genus Teleocichla appreciate similar habitats, as well. Most tetras and cichlids, and a large majority of the catfishes, can thrive under similar water conditions, particularly where the water is flowing well. Current breaks, in the form of large stones, driftwood, and the like, will also increase your options.
 

A Special Fish for a Specialized Setup

Like many fishes, this species is a bad choice for an impulse aquarium buy, but it is an excellent fish to plan around if you would like to try something new. A specialized river aquarium designed around the needs of gold nugget plecos and a few habitat-appropriate tankmates, complete with rocks and high current, can make a beautiful and fascinating display.
 
The author has created a short YouTube video showing how Baryancistrus xanthellus are collected for the aquarium trade. Check it out at https://youtu.be/QVWTev_ic_k