Apistogramma paulmuelleri

By Pet Zone SD Team • October 2026

Overview

Apistogramma paulmuelleri spent roughly three decades in the aquarium trade under a rotating cast of names before anyone gave it a proper scientific one. Per Aquarium Glaser, the fish first appeared in hobby photographs around 1982, misidentified as Apistogramma caeti and nicknamed the "Peru Apistogramma." Ingo Koslowski — a name that turns up repeatedly in the trade history of poorly known apistos — used "sp. Rotwangen" in 1985, then is credited with "sp. Masken" (German for "mask," describing its facial markings) around 2003, a label that stuck for about ten years. SeriouslyFish separately documents "sp. Apache," "sp. Peru (II)," "sp. Peru-regani," "sp. cf. regani (Belém)," and "sp. carapintada" as further names applied to the same fish or its close relatives. It wasn't until 2013 that Römer, Beninde, Duponchelle, García-Dávila, Vela-Díaz, and Renno formally described it as Apistogramma paulmuelleri in Vertebrate Zoology — naming it, per FishBase, after Professor Emeritus Dr. Paul Müller (1940–2010), a German herpetologist and zoogeographer at the University of Trier who helped establish how Neotropical cichlids came to be distributed across the continent.

Cichlidae.com (Cichlid Room Companion) adds a telling detail: the only documented aquarium-trade record it cites is a single male photographed in a German tank in June 2010, imported from Peru with no recorded collection site — a reminder that even a fish with a long, name-shifting trade history can have a thin paper trail once you look for hard documentation rather than hobby anecdote.

Identification

SeriouslyFish assigns paulmuelleri to the Apistogramma regani species group and complex, within the broader cichlid subfamily Geophaginae (Cichlinae per Cichlidae.com's classification). Its DATZ trade code is A52. Males are substantially larger and more colorful than females: SeriouslyFish describes bright red markings and metallic bluish lines across the cheeks and gill covers in mature males, with large males developing yellow-to-orange lower abdomens and more extended fin rays. In females, the lateral body band may break up into a row of oval spots rather than running solid — a useful sexing cue alongside size and fin length.

Natural Habitat

SeriouslyFish places paulmuelleri in Loreto Department, Peru, in the Amazon basin, with known localities lying east of the Itaya River and west of the Amazon mainstem, north of the town of Nauta. The type locality is a small forest stream only a few hundred meters long, 3 to 8 meters wide, up to 80cm deep, running clear and light brown. Fish sharing that stream include Laetacara flavilabris, Crenuchus spilurus, Aequidens species, Rivulus species, and a Hyphessobrycon species — useful context for picking realistic, non-Apistogramma dither fish if you want to approximate the biotope. SeriouslyFish notes the stream has had riparian (streamside) vegetation removed since 2009, and Cichlidae.com separately flags deforestation along the type locality, the Iquitos–Nauta road corridor, and Amazonia Occidental's main river channels as ongoing threats to the species.

Tank Setup

• Tank size: SeriouslyFish recommends a minimum footprint of 45x30cm (18x12in), roughly 41 liters (11 US gallons), for a single pair — a group needs meaningfully more floor space. See our tank setup guide for general dwarf cichlid dimensions and layout principles.
• Substrate & décor: Cover is essential, not optional. SeriouslyFish suggests clay flowerpots, lengths of plastic piping, or a sand bed built up with wood roots and branches to create shaded spots and caves. Dried leaf litter and alder cones both help establish blackwater-style conditions and double as spawning sites and a microbial food source for fry.
• Lighting & plants: Keep lighting dim. SeriouslyFish lists Microsorum, Taxiphyllum, Cryptocoryne, and floating Ceratopteris as suitable plant choices that tolerate the same shaded conditions.
• Filtration: Run gentle filtration — an air-driven sponge filter is specifically recommended — since SeriouslyFish describes this species as sensitive to fluctuating organic waste levels. Don't stock it into a biologically immature tank. For sizing reference, SeriouslyFish suggests a filter rated 165–205 L/h and roughly a 75–100W heater for a tank at the minimum recommended footprint.
• Water chemistry: SeriouslyFish specifies pH 4.0–6.5, temperature 22–31°C (72–88°F), and hardness 1–3 dGH — soft, acidic, warm water consistent with genus norms. See our water parameters guide for building and holding soft, acidic water safely.

Feeding

SeriouslyFish describes paulmuelleri as mainly carnivorous in the wild, feeding on benthic (bottom-dwelling) invertebrates. In the aquarium, live or frozen Artemia, Daphnia, and bloodworm are all well accepted, and most individuals eventually learn to take dried foods too — pellets are preferred over flakes for this bottom-oriented feeder. See our general feeding guide for conditioning diets ahead of a spawn.

Temperament & Compatibility

SeriouslyFish lists this species' general temperament as unknown and rates overall difficulty at 6 out of 8 — moderate, and dependent on a genuinely mature, stable tank rather than beginner-friendly forgiveness. It's best kept as a single pair, alone or alongside small dither fish such as Nannostomus species. As with every species on this site, avoid mixing it with other Apistogramma to prevent hybridization and unnecessary territorial conflict.

Breeding

Paulmuelleri is a substrate and cavity spawner, not a mouthbrooder. SeriouslyFish describes it laying eggs in crevices or cavities among the tank's décor, with the female taking the lead on egg and fry care while the male's role is more peripheral. In a smaller tank, SeriouslyFish specifically warns that the male may need to be removed once spawning begins, since the female can become highly aggressive defending the brood — a more pointed warning than this site typically sees for other Apistogramma species, and worth planning for before you pair this one up. Follow our general breeding guide for the broader conditioning-to-fry-rearing process, adjusting for the extra caution around the male's safety here.

Sourcing Notes

This is not a species you'll find at a general fish store. Cichlidae.com's own documentation cites essentially one confirmed trade record — a single photographed male from 2010 — and even its decades of trade under names like "sp. Masken" and "sp. Apache" reflect a thin, specialist supply chain rather than steady retail availability. If you do find stock offered under any of its historical trade names, treat the name itself with some skepticism: SeriouslyFish specifically notes that "Apache" has been applied to other, unrelated Apistogramma populations as well, so a trade name alone doesn't confirm you're getting true paulmuelleri. Given the size discrepancy covered in the FAQ below, also don't take a seller's size claim at face value without asking where their stock was collected or bred. See our general sourcing guide for broader guidance on verifying identification and acclimating new, hard-to-find stock.

Final Thoughts

Paulmuelleri is a case study in how slowly taxonomy can catch up with the aquarium trade: three decades, at least seven different names, and a single confirmed trade photograph on record, before science finally gave it one name that actually sticks. Add a Data Deficient conservation rating, documented habitat degradation at its type locality, and a size claim from one source that nearly doubles the other two, and you get a fish that rewards a keeper willing to track down specialist stock and read past the first search result — not one to buy on a whim from a tank labeled with whatever trade name happens to be printed. If you want a far more thoroughly documented, widely available species to start with instead, try cacatuoides or nijsseni. If this site's taxonomic-mess entries are what drew you in, paulmuelleri sits comfortably alongside commbrae and norberti.

Frequently Asked Questions

Why was Apistogramma paulmuelleri sold under so many different names?

Because nobody had formally described it. According to Aquarium Glaser, the fish first reached the hobby around 1982 as photographs in the hobby press, where it was initially identified — apparently incorrectly — as Apistogramma caeti and nicknamed the "Peru Apistogramma." Ingo Koslowski used the trade name "sp. Rotwangen" in 1985, and is credited with coining "sp. Masken" (German for "mask," after its facial markings) around 2003; that name stuck for roughly a decade. SeriouslyFish separately lists "sp. Apache," "sp. Peru (II)," "sp. Peru-regani," "sp. cf. regani (Belém)," and "sp. carapintada" as further trade names applied to the same complex. The fish wasn't given its current scientific name until Römer, Beninde, Duponchelle, García-Dávila, Vela-Díaz & Renno described it as Apistogramma paulmuelleri in 2013 — roughly three decades after hobbyists first saw it. SeriouslyFish also notes that "Apache" has separately been applied to other, non-conspecific Apistogramma populations, so that particular trade name is not a reliable identifier on its own.

Who was paulmuelleri named after?

Professor Emeritus Dr. Paul Müller (1940–2010), a German herpetologist and zoogeographer who served as Professor of Biology at the University of Trier. Per FishBase, the describing authors chose the name to honor his contributions to understanding the biogeographic origins of Neotropical cichlids — the same broad field their own paper addresses.

How big does Apistogramma paulmuelleri get?

SeriouslyFish gives males up to about 42mm (1.7in) standard length and females up to about 33mm (1.3in) — figures that line up closely with FishBase's separate 4.1cm standard-length maximum for males. A third source, Aquarium Glaser, states males reach roughly 8cm and females roughly 5cm — nearly double the other two sources' numbers, with no other source corroborating it. Since the two independent, aquarium-specific sources agree closely with each other, this guide treats the Aquarium Glaser figure as an outlier rather than fact, and uses the SeriouslyFish/FishBase range (roughly 1.3–1.7 inches) as the realistic adult size.

Is Apistogramma paulmuelleri endangered?

It carries an IUCN Red List status of Data Deficient, per a 2016 assessment reported by Cichlidae.com (Cichlid Room Companion) — not enough is known to classify its risk level with confidence. Cichlidae.com notes the describing researchers (Römer et al.) found it less abundant than other Apistogramma populations they studied in Peru, and flagged deforestation at the type locality, along the Iquitos–Nauta road, and along main Amazonia Occidental river channels as threats, recommending ongoing population monitoring. Separately, Aquarium Glaser notes the type stream itself has seen riparian vegetation removed since 2009. Data Deficient is not the same as a clean bill of health — it means the data to assess the species properly doesn't yet exist.