Apistogramma megastoma

By Pet Zone SD Team • October 2026

Overview

Apistogramma megastoma is one of only two Apistogramma species documented as a mouthbrooder — and for most of its time in the hobby, buyers and even researchers didn't realize it was its own species at all. It was traded for years under the name A. sp. "Kelleri" (also sold as "Diamond Face"), and before it was formally described, the "Kelleri" fish was treated by researchers as a population of A. barlowi — the genus's other mouthbrooder. A 2017 description by Uwe Römer and co-authors in the journal Vertebrate Zoology separated the two for good, based on specimens collected from small forest streams feeding the Jutaí drainage in Peru's Loreto region, near the Peru–Colombia–Brazil border close to Leticia. See Breeding below for how its mouthbrooding differs from barlowi's.

The "Kelleri" name has outlasted the formal description by the better part of a decade. As of this writing, SeriouslyFish's own Apistogramma genus page still lists A. sp. "Kelleri" as its own separate profile, distinct from megastoma — and most retailers selling this fish still lead with "Kelleri" or "Diamond Face" rather than the 2017 scientific name. It's a different kind of labeling problem than the ones covered on our sourcing page: not confusion between two existing species, and not scarcity, but a trade name that simply never got updated after the fish it refers to was given a real one.

Color & Identification

Megastoma's defining feature is in its name: mega + stoma, Greek for "big mouth." Both sexes carry a noticeably large head and oversized jaws relative to body size — even more pronounced than barlowi's — which the original description ties directly to its mouthbrooding habit. The caudal fin is lyrate (forked) and densely banded, and overall coloration shifts with age, mood, and sex. Megastoma and barlowi are close enough in appearance to have been confused by researchers themselves prior to 2017; the two are told apart mainly by color pattern details and by differences in the number of scale rows across the cheek, not by any single obvious marking.

Tank Setup

Retailers generally recommend a 26-gallon minimum for a single pair, somewhat larger than the smaller blackwater specialists on this site, reflecting megastoma's bigger adult size. Standard soft-water apisto setup applies:

• Substrate: Soft, fine sand or fine gravel.
• Hardscape: Caves, flowerpots, or driftwood roots for cover and shelter, even though a mouthbrooding female doesn't guard a fixed nest the way a cave-spawning apisto does.
• Leaf litter: Catappa or oak leaf litter adds cover and tannins consistent with its blackwater origin.
• Planting and light: Dim lighting with soft-water-tolerant plants — the same genus-wide approach covered on our tank setup page.
• Maturity: Let the tank cycle and stabilize fully before adding fish; blackwater species in general handle a freshly set up tank poorly.

Feeding

Carnivorous, in line with the rest of the genus. Live or frozen Artemia (brine shrimp), Daphnia, Moina, and chironomid larvae (bloodworm) make up the core of a good diet, with most individuals eventually accepting a quality pellet once settled. Several small feedings a day suit this species better than one large one — see our general feeding guide for the genus-wide reasoning.

Temperament & Compatibility

Described by retailers as mostly peaceful, though documentation is thinner here than for widely kept species like cacatuoides simply because far fewer hobbyists have kept it — another consequence of it only recently sorting out from under the barlowi/"Kelleri" confusion. As with barlowi, small, calm dither fish are a safer bet than mixing it with other Apistogramma species.

Breeding

Megastoma and barlowi are the genus's only two documented mouthbrooders, and they don't brood the same way. Barlowi is a facultative biparental mouthbrooder — either the male, the female, or both may carry eggs, and it doesn't happen every spawn. Megastoma is described in its original scientific description as an exclusively maternal, larvophilic mouthbrooder: only the female carries the brood, and she does so through the larval stage rather than releasing free-swimming fry straight away. This is a firmer, less variable strategy than barlowi's, and it's consistent with megastoma's proportionally larger mouth and head — a female built to carry a full brood rather than sometimes handing the job to a male.

Because the brood rides in the mother's mouth rather than sitting in an open or enclosed nest, it's shielded from a lot of the ammonia and nitrite swings that our genus-wide breeding guide flags as the biggest fry-stage failure point for cave spawners. The tradeoff is the same one that applies to any mouthbrooder: a stressed or disturbed female can abandon or swallow a brood, so a calm, undisturbed tank matters more here than it does for a species guarding a fixed cave.

Sourcing Notes

Megastoma moves through the same specialist apisto and cichlid importer channels as barlowi, and almost always under its older trade names — A. sp. "Kelleri" or "Diamond Face" — rather than the 2017 scientific name. If you're specifically after one of the genus's two mouthbrooders, don't assume a "mouthbrooding apisto" listing is automatically barlowi; ask the seller which species it actually is, since the two were only separated in the scientific literature within the last decade and plenty of listings still haven't caught up. See our general sourcing guide and the community page for where dedicated apisto importers and breeders tend to surface.

Final Thoughts

Megastoma is worth knowing about even if you end up keeping barlowi instead, because the two are genuinely easy to mix up — researchers did it first. For a keeper who already wants the genus's mouthbrooding exception but wants the version with firmer, maternal-only brood care and a bigger adult fish, megastoma is the one to specifically ask for by its real name, not just "the mouthbrooder." Like barlowi, it rewards someone who wants behaviorally different rather than just chemically harder.

Frequently Asked Questions

Is Apistogramma megastoma the same fish as the trade name "Kelleri"?

Yes. "Kelleri" (sometimes sold as "Diamond Face") was a hobby trade name used for years before this fish had a scientific name — and before its 2017 description, researchers had even treated it as a population of A. barlowi. The formal description separated it into its own species, Apistogramma megastoma, but the trade name never fully went away: specialist sites and retailers still list "sp. Kelleri" stock nearly a decade later, so the same fish can show up under either name depending on where you're buying it.

How is megastoma different from Apistogramma barlowi?

They're the genus's only two documented mouthbrooders and are closely related enough to be confused, but they brood differently. Barlowi is a facultative biparental mouthbrooder — either parent may carry the eggs, and it doesn't always happen. Megastoma is an exclusively maternal mouthbrooder — only the female carries, and her mouth and head are proportionally even larger than barlowi's to do it, which is where the name comes from (Greek for "big mouth"). The two also differ in color pattern and in the number of scale rows on the cheek.

What water parameters does Apistogramma megastoma need?

Soft and acidic blackwater: pH 4.8–6.5 and 75–82°F (24–28°C). It comes from small forest streams in the Loreto region of northeastern Peru, near the Peru–Colombia–Brazil border, the same general blackwater habitat type as several other advanced species on this site. Give it a mature, stable tank rather than a freshly cycled one.

How big does Apistogramma megastoma get?

Males reach roughly 3 inches (7.6cm standard length); females stay smaller, around 2.4 inches (6.2cm). Retailers often quote a slightly larger total-length figure of about 3.7 inches, which is normal — total length includes the tail fin and always runs a bit longer than standard length. Either way, it's one of the larger-bodied species in this genus's trade.

Where can you buy Apistogramma megastoma?

Specialist cichlid and apisto importers carry it occasionally, usually labeled with its older trade name "Kelleri" or "Diamond Face" rather than the scientific name. It isn't a general-retail fish. Ask specifically whether the stock is A. megastoma / "Kelleri" rather than assuming a "mouthbrooding apisto" listing means A. barlowi — the two are easy to conflate precisely because researchers themselves did so before 2017.