Freshwater Flounder (Trinectes Maculatus)
Freshwater Flounder (Trinectes maculatus)
The Freshwater Flounder is a flatfish that offers a truly unique silhouette for the bottom layer of an aquarium. Naturally found in coastal estuaries along the Atlantic coast, they are born looking like "normal" fish but undergo a metamorphosis where one eye migrates to the other side, and they become bottom-dwelling specialists. While they are sold as freshwater fish, they are highly hardy and interesting "sit-and-wait" predators that require a specific environment to thrive long-term.
Key Information
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Common Name: Freshwater Flounder, Hogchoker
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Scientific Name: Trinectes maculatus
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Origin: North & Central America (Atlantic Coastal Waters)
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Max Size: 10–15 cm
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Lifespan: 5–10 years
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Temperament: Peaceful (Will eat very small tank mates)
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Diet: Carnivore – Prefers live or frozen bloodworms, blackworms, and brine shrimp. They rarely accept dry flakes.
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Care Level: Moderate
Water Parameters
| Parameter | Value |
| Temperature: | 20–28°C |
| pH: | 7.0–8.5 |
| Hardness: | 10–20 dGH |
| Salinity: | Prefers low-end Brackish (1.002–1.005 SG) as they age. |
| Minimum Tank Size: | 75L+ |
Behaviour & Tank Compatibility
Flounders are peaceful and largely inactive during the day, remaining buried in the sand with only their eyes visible. They are best housed with other peaceful, non-aggressive species that inhabit the upper layers of the tank. Ideal tank mates include Mollies, Guppies, and Knight Gobies, all of which can tolerate the slightly brackish conditions that Flounders prefer. Avoid keeping them with aggressive bottom-dwellers or large crabs that might pinch their soft bodies.
Ideal Tank Setup
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Soft Sand Substrate: Essential. They must be able to bury themselves to feel secure. Coarse gravel or sharp rocks will damage their underside and cause infections.
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Open Floor Space: They need a large footprint of sand rather than a tall tank. Avoid cluttering the bottom with too many ornaments.
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Stable Water Conditions: They are sensitive to high nitrates and ammonia. Excellent filtration and regular water changes are required.
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Dim Lighting: They are more active and comfortable in lower light or tanks with plenty of floating plant cover.
Why Choose the Freshwater Flounder?
The Freshwater Flounder is for the "collector" who enjoys watching natural camouflage in action. There is something incredibly rewarding about spotting their eyes peeking out from the sand or watching them suddenly glide across the bottom like a shadow. For an aquarist with a sand-bottomed setup, they provide a prehistoric and quirky aesthetic that standard community fish simply cannot offer.
Description
Freshwater Flounder (Trinectes maculatus)
The Freshwater Flounder is a flatfish that offers a truly unique silhouette for the bottom layer of an aquarium. Naturally found in coastal estuaries along the Atlantic coast, they are born looking like "normal" fish but undergo a metamorphosis where one eye migrates to the other side, and they become bottom-dwelling specialists. While they are sold as freshwater fish, they are highly hardy and interesting "sit-and-wait" predators that require a specific environment to thrive long-term.
Key Information
-
Common Name: Freshwater Flounder, Hogchoker
-
Scientific Name: Trinectes maculatus
-
Origin: North & Central America (Atlantic Coastal Waters)
-
Max Size: 10–15 cm
-
Lifespan: 5–10 years
-
Temperament: Peaceful (Will eat very small tank mates)
-
Diet: Carnivore – Prefers live or frozen bloodworms, blackworms, and brine shrimp. They rarely accept dry flakes.
-
Care Level: Moderate
Water Parameters
| Parameter | Value |
| Temperature: | 20–28°C |
| pH: | 7.0–8.5 |
| Hardness: | 10–20 dGH |
| Salinity: | Prefers low-end Brackish (1.002–1.005 SG) as they age. |
| Minimum Tank Size: | 75L+ |
Behaviour & Tank Compatibility
Flounders are peaceful and largely inactive during the day, remaining buried in the sand with only their eyes visible. They are best housed with other peaceful, non-aggressive species that inhabit the upper layers of the tank. Ideal tank mates include Mollies, Guppies, and Knight Gobies, all of which can tolerate the slightly brackish conditions that Flounders prefer. Avoid keeping them with aggressive bottom-dwellers or large crabs that might pinch their soft bodies.
Ideal Tank Setup
-
Soft Sand Substrate: Essential. They must be able to bury themselves to feel secure. Coarse gravel or sharp rocks will damage their underside and cause infections.
-
Open Floor Space: They need a large footprint of sand rather than a tall tank. Avoid cluttering the bottom with too many ornaments.
-
Stable Water Conditions: They are sensitive to high nitrates and ammonia. Excellent filtration and regular water changes are required.
-
Dim Lighting: They are more active and comfortable in lower light or tanks with plenty of floating plant cover.
Why Choose the Freshwater Flounder?
The Freshwater Flounder is for the "collector" who enjoys watching natural camouflage in action. There is something incredibly rewarding about spotting their eyes peeking out from the sand or watching them suddenly glide across the bottom like a shadow. For an aquarist with a sand-bottomed setup, they provide a prehistoric and quirky aesthetic that standard community fish simply cannot offer.
