Taxonomy & naming
Elassoma evergladei was described by David Starr Jordan in 1884 from two Florida collections made by R. E. Earll — Lake Jessup near Sanford and the Indian River near Titusville — published in the Proceedings of the United States National Museum. The type series is held at the Smithsonian (USNM): eight syntypes from Lake Jessup and originally three, now one, from the Indian River. Elassoma orlandicum Lönnberg, 1894, described a decade later from central Florida, is now treated as a junior synonym of E. evergladei.
The species is the type of the genus Elassoma, the only genus in the family Elassomatidae, which current classifications and the Catalog of Fishes place in the order Centrarchiformes alongside the true sunfishes, Centrarchidae. Pygmy sunfishes are not miniature sunfishes, however — they are a distinct lineage, and earlier authors linked them instead with the sticklebacks and pipefishes on the strength of shared skeletal features. Elassoma zonatum, the banded pygmy sunfish, is the type species of the family; embedded rather than exposed scales on top of the head help distinguish E. evergladei from several of its congeners.
Morphology
Elassoma evergladei is one of the smallest vertebrates kept in aquaria, reaching about 1.5 in total length at most and averaging closer to 1 in. The body is deep for its length and laterally compressed, carried on a rounded, fan-shaped caudal fin rather than a forked one, and — as in the rest of the family — it has no lateral line; sensory pits on the head and body stand in for the canal system found in most bony fishes. Scales are embedded rather than raised, giving the skin a smooth, almost naked look.
Outside the breeding season both sexes wear the same drab, effective camouflage: mottled brown backs fading to cream or pale reddish-brown below, broken by faint flecks that dissolve the fish's outline against leaf litter and moss. A breeding male abandons all of that. His body turns jet black from nose to tail, and along the flanks scatter a dust of iridescent blue to blue-green spots that flash as he turns — a display built for the dim, tannin-stained water he lives in. Females keep their everyday brown-and-cream pattern even at spawning time, and this contrast between plain female and blackened, spangled male is the clearest field mark for telling the sexes apart.
Habitat
The Everglades pygmy sunfish ranges the Atlantic and Gulf coastal plain from the Cape Fear River drainage in North Carolina south through peninsular Florida to the edge of the northern Everglades, and west to Mobile Bay, Alabama — one of the broadest ranges of any Elassoma species. Across that range it keeps to still or barely moving water: swamps, densely vegetated sloughs, sluggish blackwater streams and shallow ponds, typically over a soft mud bottom and hidden among submerged plants.
These waters are shaded, stained acid-brown by decaying leaf litter, and low in current, and they swing with the seasons — cool in winter, warm through the Florida summer. FishBase reports a tolerance from 50–86 °F in the wild, a spread wide enough that most of the coastal plain's Elassoma habitat never needs artificial heating, which is close to how the species is kept.
Feeding
In the wild, Elassoma evergladei is a micropredator that picks worms, small crustaceans and aquatic insect larvae from among the plants it hides in, rather than chasing prey through open water. Its mouth is small and upturned, built for taking these live morsels one at a time.
That preference carries straight into the aquarium: this is a live-food fish first. Small frozen foods — baby brine shrimp, mini-bloodworm, cyclops and daphnia — and live foods such as brine shrimp or mosquito larvae are readily taken, and high-quality flake or micro-pellet can supplement a diet once fish are conditioned to it, though dry food is often refused by fish new to the aquarium. Because of its size, several small meals through the day suit it better than one large feeding.
Mating
Breeding males stake out and defend an individual patch of dense vegetation rather than forming pairs or schools, driving off rival males that intrude. Coloration does the courting: a male in breeding dress turns almost entirely black and flashes his blue-green spots at a female, displaying and shepherding her toward his chosen mossy territory. Because the species tolerates cool water for much of the year, this display and the spawning that follows are often cued by a rise in temperature, with the hobby's usual target for triggering activity around 79 °F.
Breeding
Elassoma evergladei is an egg-depositor. The female lays adhesive eggs a few at a time among the fine leaves of aquatic plants — Ceratophyllum, hornwort, is singled out as a favorite — rather than releasing them into open water, and a single spawning can scatter 40 to 60 eggs through the vegetation. The eggs hatch quickly, in about two to three days, and the fry take infusoria as a first food before graduating to newly hatched brine shrimp.
Parents generally do not target the eggs and fry, though cautious keepers often remove the adults after spawning rather than risk it. Published sources consulted for this profile do not report a specific lifespan for the species.
In the aquarium
Elassoma evergladei suits an unheated or lightly heated species tank rather than a tropical community — its natural range sees water anywhere from about 50–86 °F, and most keepers run tanks at ordinary room temperature, warming only to around 79 °F to encourage spawning. Dense planting is not optional: thickets of Java moss or fine-leaved plants such as hornwort give the fish the cover it uses constantly, break sightlines between territorial males, and double as spawning substrate.
Because it depends on small live and frozen foods and is easily outcompeted at the surface, this is not a community fish. Larger or faster tankmates will out-feed it and may treat a 1 in fish as a snack; shrimp such as Neocaridina and small snails make safer companions, or the species can simply be kept alone in a densely planted nano tank, which is how most experienced keepers spawn it. It breeds readily under these conditions and has become a mainstay of the North American native-fish hobby, traded within the United States and increasingly available in Europe.
Conservation
The IUCN Red List assessed Elassoma evergladei as Least Concern in 2013, citing its large range, numerous populations and stable numbers. It carries no federal protection status in the United States and is not listed under the Endangered Species Act.
The threat identified for the species is habitat loss from the drainage and modification of the wetlands it depends on, a pressure shared by many coastal-plain endemics, though the assessment found the species' overall status to be stable rather than declining. It remains common enough across its range to support an aquarium trade in both the United States and Europe without evident harm to wild populations.