Anaspidoglanis macrostomus

The Fat-mouth Catfish is a large and robust bottom-dweller from Africa, named for its characteristically wide mouth. Due to its significant adult size, it requires a spacious aquarium and is not suitable for small community tanks. This fish is known to be territorial, so it's best kept either by itself or with other large, fast-swimming fish that occupy the middle and upper levels of the water. You should avoid keeping it with other bottom-dwellers, as it will likely become defensive and aggressive towards them.

This catfish has a moderate activity level and enjoys exploring the tank's lower regions. It has a natural habit of digging in the substrate while searching for food, which can easily uproot delicate aquatic plants. If you wish to have plants, it is best to choose tough, hardy species like Anubias or Java Fern and attach them to rocks or driftwood instead of planting them in the gravel. As an omnivore, it is not a fussy eater. A balanced diet of high-quality sinking pellets, supplemented with occasional frozen or live foods, will keep it healthy and active. Because it is a large fish that produces a lot of waste, a powerful filtration system and regular water changes are absolutely essential to maintain a clean and healthy environment. With proper care, it can be a part of your aquarium for a decade.

The Fat-mouth Catfish, Anaspidoglanis macrostomus, is an engaging and characterful species for the dedicated aquarist with the resources to house it properly. Originating from African river systems, it has evolved to be a hardy and resilient fish, which is reflected in its tolerance for a broad range of water hardness and a relatively neutral pH. The 'medium' difficulty rating is not due to chemical sensitivity, but rather its substantial physical and behavioral requirements. Its considerable adult size and high waste production necessitate a robust filtration system, ideally a large canister filter or a sump, to effectively manage the significant bioload and maintain pristine water conditions with low nitrate levels. The specified need for medium water flow replicates its natural riverine habitat, promoting water oxygenation and aiding in sweeping waste from the substrate level where the fish resides.

Socially, this species is best described as solitarily territorial. While it does not typically hunt other fish, it will claim a specific area, often centered around a cave or a large piece of driftwood, and vigorously defend it from any perceived intruders. This is especially true for other bottom-dwelling species or similarly shaped catfish. Consequently, tank mate selection is a critical decision. Ideal companions are large, robust, and occupy different water columns, such as larger characins or peaceful cichlids that are too large to be intimidated or seen as food. Keeping more than one A. macrostomus is generally ill-advised unless the aquarium is exceptionally large (well over 500 liters) with multiple distinct territories and visual barriers to mitigate conflict.

The catfish's interaction with its environment is a key aspect of its husbandry. Its classification as a 'plant rooter' means it is an active digger, constantly sifting through the substrate for leftover food morsels. This innate behavior will quickly uproot any standard rooted plants like Vallisneria or Cryptocoryne. Therefore, aquascaping should focus on hardscape elements like large stones and driftwood to create caves, overhangs, and defined territories. For greenery, epiphytic plants such as Anubias, Bolbitis, or Java Fern attached securely to the hardscape are the most viable options. Floating plants can also be utilized to diffuse overhead lighting, which is often appreciated by this nocturnal and bottom-oriented species.

Feeding should be diverse to satisfy its omnivorous diet. A high-quality sinking pellet or wafer should form the staple of its nutrition. This should be supplemented two to three times per week with protein-rich frozen foods like bloodworms, krill, or mysis shrimp, and occasional live foods such as earthworms or nightcrawlers to encourage natural foraging behavior. The recommended feeding frequency of 'alternate days' is an excellent guideline to prevent overfeeding and obesity, which can be an issue in these voracious eaters, and it also helps manage their high waste output. Breeding in the home aquarium is exceptionally rare and considered very difficult, likely requiring specific environmental triggers related to seasonal changes that are not yet fully understood or easily replicated.

Anaspidoglanis macrostomus is a freshwater teleost within the family Claroteidae, a group of catfishes endemic to the Afrotropical realm. The species epithet is descriptive, derived from Greek: macros (large) and stoma (mouth), referencing its distinctively wide gape, which is an adaptation for its omnivorous feeding strategy. As a member of the order Siluriformes, it shares key characteristics with other catfishes, including its benthic lifestyle. Its current IUCN Red List status as 'Least Concern' (LC) indicates that wild populations are considered stable and not facing immediate, significant threats, though habitat degradation could pose future risks.

Ecologically, A. macrostomus occupies a niche in benthic zones of riverine habitats. Its physiology is adapted for environments with moderate water currents, explaining its preference for medium flow in captive settings to ensure adequate dissolved oxygen levels and prohibit the accumulation of detritus. The species exhibits a notable euryhaline capacity for a primary freshwater fish, tolerating a wide range of water hardness (36-268 ppm dGH) and total dissolved solids (up to 299 ppm), which points to highly efficient osmoregulatory function. Its pH tolerance (6.5-7.5) around neutral is typical for many large river systems with significant buffering capacity.

Behaviorally, the species displays pronounced territoriality, a common resource-defense polygyny strategy in benthic Siluriformes that compete for limited resources such as shelter and foraging grounds. This behavior has significant implications for its management in a captive environment, generally necessitating solitary housing or an exceptionally large enclosure with complex structural elements (e.g., caves, driftwood) to create visual barriers and mitigate agonistic encounters. Its moderate activity level combined with a medium metabolic rate underpins a feeding schedule of alternate days, aligning with an opportunistic benthic omnivore's feeding pattern. Its foraging behavior, described as 'plant rooting', involves significant bioturbation of the substrate, an ecological process where the organism actively reworks sediment while searching for invertebrates, algae, and detritus.

From a husbandry perspective, the species presents a high bioload factor (13) and consequently high nitrogenous waste production. These parameters demand a filtration system with a high turnover rate and substantial capacity for both mechanical and biological processing to maintain water quality and prevent chronic toxicity. The reported difficulty in captive breeding suggests complex reproductive cues, possibly tied to seasonal environmental shifts such as changes in photoperiod, temperature drops simulating rainy seasons, altered flow rates, or the presence of specific pheromonal signals—all of which are challenging to replicate accurately in an artificial system. The decadal lifespan is indicative of a K-strategist life history, characterized by slower growth, longer life, and larger body size.