Tonguetied minnow
Exoglossum laurae
The Tonguetied minnow features a slender body, striking bluish-silver coloration, and distinctive ventral barbels.
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About the Tonguetied minnow
Exoglossum laurae (tonguetied minnow) is a freshwater leuciscid minnow of cool, clean, rocky streams in parts of the eastern United States. It has a distinctive ventral mouth adapted for benthic feeding, and it is associated with pebble/rock nest spawning behavior documented for Exoglossum in scientific literature.
Also known as
Quick Facts
Size
16 cm
Temperament
Peaceful
Difficulty
Advanced
Min Tank Size
30 gallons
Lifespan
1-4 years
Origin
North America (eastern United States; disjunct in upper Ohio River basin incl. Allegheny, upper New River drainage, and Great Miami/Little Miami systems; also reported in upper Genesee River, NY/PA)
Diet
Omnivore leaning insectivore - insect larvae and other small invertebrates; will also graze benthic foods (offer small sinking pellets, frozen foods, and live insect larvae)
Water Parameters
18-20°C
6.5-8
4-15 dGH
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Calculate heater sizeCare Notes
- Give them a long tank with real current (powerhead or strong canister return) and lots of oxygen - they act stressed and sulky in still water.
- Keep it cool and well-oxygenated with excellent filtration and regular water changes; this species is associated with clean, rocky, flowing waters and does poorly in degraded conditions.
- Use sand or small rounded gravel and add piles of smooth stones; they spend a lot of time picking and rubbing around the bottom and hate sharp substrate.
- Feed like a stream fish: frozen bloodworms, blackworms, daphnia, and small sinking pellets, but do it in small doses so food does not rot in the rocks.
- They do best in a group (5-8+) or they get jumpy, and you need a tight lid because they will launch when spooked.
- Tankmates: think other cool-water, current-loving minnows and darters; skip slow fancy fish and anything nippy because tonguetieds get bullied and stop eating.
- Breeding can be encouraged by mimicking spring conditions; spawning is reported mid-May to mid-June at ~18–20°C, and Exoglossum uses pebble/rock nest substrates.
Compatibility
Good Tankmates
- Other peaceful native minnows and shiners (like rosyface shiners, satinfin shiners, or plain old dace) - they school up, stay busy, and nobody gets singled out. Keep a small group so the tonguetieds chill out and act natural.
- Hillstream-type buddies and current lovers (rainbow shiners, darters if your tank is cool and well-oxygenated) - these guys like similar flow and clean water, and they tend to ignore each other.
- Other cool-water, high-oxygen, current-tolerant fishes with similar environmental requirements.
- Suckermouth algae grazers that keep to themselves (bristlenose pleco, otocinclus in a mature tank) - different job in the tank, minimal drama. Just make sure there is food on the bottom for everyone.
- Cool-water, high-oxygen species that tolerate current; avoid warmwater/tropical community fish if maintaining the species at cool, stream-like temperatures.
- Calm, non-predatory sunfish relatives only if you really know your fish (pygmy sunfish in a planted setup) - sometimes works because they are not big chompers, but watch feeding time since tonguetieds are quick to the groceries.
Avoid
- Big predators and anything with a mouth made for minnows (largemouth-type bass, pike, big catfish) - if it can swallow a tonguetied, it will eventually test that theory.
- Nippy, pushy fish that turn peaceful tanks into a mosh pit (tiger barbs, serpae tetras, most 'semi-aggressive' stuff) - tonguetieds are peaceful, but they are always on the move and can get harassed or stressed in a rough crowd.
- Slow fish with fancy fins (bettas, longfin guppies, fancy goldfish) - the minnow is too active and the temp/flow goals usually do not line up, plus fin-nippers in the mix is just asking for problems.
- Territorial bottom bruisers (most cichlids, especially convict-type and anything that guards a cave) - tonguetieds forage along the bottom and will blunder into claimed turf all day long, which gets them chased nonstop.
Where they come from
Tonguetied minnows (Exoglossum laurae) are North American stream fish. Think cool, clear runs with gravel and cobble, lots of current, and a steady supply of little bugs drifting by. They are built for life on the bottom and in the flow, not for warm, still community tanks.
If you have kept darters or other stream cyprinids, the general vibe is similar: high oxygen, clean water, and structure on the bottom matter more than plants and pretty decor.
Setting up their tank
This is one of those fish where the tank has to match the fish, not the other way around. Give them a long footprint and real flow. A 40 breeder is a nice starting point for a small group, but bigger is easier because the water stays stable and you can spread out territories.
- Tank size: 40 breeder minimum for a group, 55-75+ is better if you want them to settle in and show normal behavior
- Temp: cool side of freshwater (roughly mid 60s to low 70s F). They do not love tropical temps long-term
- Flow: strong, directional flow with dead spots reduced (powerheads or a stream manifold work great)
- Filtration: oversized and oxygen-heavy (big HOB + powerhead, or a canister with a spray bar)
- Substrate: smooth gravel, small cobble, and a few larger rounded rocks. Skip sharp stuff
- Cover: rock piles, slate ledges, driftwood pinned down well, and open lanes of current to forage in
- Lighting/plants: moderate light is fine; hardy plants can work in calmer corners, but do not count on a lush planted look in a river tank
They look happiest when you build them a 'feeding lane': a long stretch of moderate-to-strong current over gravel where food naturally tumbles. They learn fast and will station up like little trout.
Warm, still tanks are where people lose them slowly. They might eat and seem fine for a while, then you start seeing stress, low stamina, and random losses. Cool water plus high oxygen makes a huge difference.
What to feed them
Tonguetieds are not picky once they settle, but they are not great at competing with hyperactive midwater pigs. In my tanks they do best with foods that sink and drift along the bottom so they can do what they are built to do: forage and grab.
- Staples: high-quality sinking pellets (small to medium), sinking bug-based granules
- Frozen: bloodworms, brine shrimp, mysis, chopped krill, daphnia (rotate, do not spam just one)
- Live (if you can): blackworms, live daphnia, small earthworm bits, insect larvae from safe sources
- Occasional: repashy-style gel foods pressed onto rocks, so they can pick at it
I feed smaller amounts more often rather than one big dump. Two small feedings a day keeps weight on them without turning the tank into a nitrate factory. Watch bellies: you want them gently rounded, not pinched.
If they are shy at first, feed after lights-out with a dim room light. Once they learn your routine, they come out readily, especially if food consistently lands in the same current lane.
How they behave and who they get along with
They are bottom-oriented, alert, and a bit territorial around favorite rocks. Not murderous, but you will see posturing and little chases, especially between males. A group spreads out the tension better than keeping a single fish with one rival.
- Good tankmates: other coolwater stream fish that like flow (many shiners, dace, some suckers, hillstream-style loaches in cooler setups)
- Use caution: aggressive bottom fish that claim the same real estate (bigger loaches, some cichlids, anything that bullies at feeding time)
- Avoid: warmwater tropical community mixes, slow fancy fish, long-finned fish, and anything that needs calm water
The main compatibility issue is not 'will they fight', its 'will your tankmates steal every bite' and 'does everyone want the same water'. If you see them hanging back and losing weight, it is usually a feeding competition problem.
Do not pair them with super pushy midwater feeders unless you are ready to target feed. Tonguetieds can be right there but still lose out if the tank is full of fast, frantic eaters.
Breeding tips
Breeding them in a home aquarium is possible but not a casual 'oops babies' situation. They tend to cue off seasonal changes. In practice that means a cool period, then a gradual warm-up with heavier feeding, plus the right substrate and flow.
- Group size: start with 6+ so you have a shot at both sexes and more natural behavior
- Seasonal cue: a winter cool-down (cooler water, shorter photoperiod) followed by spring warming
- Spawning setup: clean gravel/cobble, strong oxygenation, and plenty of stable rocks
- Conditioning: lots of frozen/live foods for a few weeks before you expect spawning activity
- Egg/fry survival: plan for predators - adults and tankmates will snack on eggs and tiny fry
If you are serious about raising fry, a separate breeding tank or at least an egg-safe zone (rock pile over coarse gravel with a screen or mesh barrier) saves you a lot of heartbreak.
Common problems to watch for
Most problems trace back to the same few things: warm water, low oxygen, and messy tanks. These fish come from clean, moving water, so they react fast when conditions slide.
- Slow decline in warm tanks: reduced appetite, lethargy, and unexplained losses over weeks
- Low oxygen signs: hanging in the highest flow, rapid gill movement, acting 'tired' despite clean-looking water
- Feeding issues: getting outcompeted and going skinny even though you feed plenty
- Bottom abrasions/infections: from sharp substrate or rough decor combined with mediocre water quality
- Parasites on new fish: flashing, clamped fins, weight loss (quarantine helps a lot)
If you see gasping or heavy breathing, treat it like an emergency: add aeration, increase surface agitation, and check temperature right away. Stream fish can crash fast when oxygen dips.
My routine that keeps them looking good is boring but effective: big filtration, strong flow, weekly water changes, and not letting uneaten food rot in the rocks. If you keep the tank clean and cool and you feed like a stream (little bits drifting by), they reward you with really cool behavior.
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