Mekran ponyfish
Deveximentum mekranense
Mekran ponyfish exhibit a slender body with silvery sides and a prominent, elongated dorsal fin adorned with dark edges.
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About the Mekran ponyfish
This is a small ponyfish from the Gulf of Oman off Iran, and like other ponyfishes its whole vibe is being a little bottom-hugging, silvery coastal fish. It is a pretty recent species description (2021), and its natural range is very localized, so you are not going to see it come through the aquarium trade in any normal way. If you ever did encounter one, you would treat it like a delicate wild marine schooling fish rather than a typical hardy "saltwater beginner" fish.
Quick Facts
Size
7.7 cm SL
Temperament
Peaceful
Difficulty
Expert
Min Tank Size
40 gallons
Lifespan
unknown
Origin
Western Indian Ocean (Gulf of Oman, Iran)
Diet
Carnivore/micro-predator - tiny crustaceans and worms; would take small frozen foods if acclimated
Water Parameters
24-28°C
8-8.4
8-12 dGH
Need a heater for this species?
This species needs 24-28°C in a 40 gallon tank. Use our heater calculator to find the right wattage.
Calculate heater sizeCare Notes
- Give it a big footprint and calm flow - think 4 ft tank minimum with open sand flats and a few low rock piles, not a packed reef wall.
- Keep salinity stable at 1.024-1.026 and temp around 24-26 C (75-79 F); they get twitchy fast when salinity or pH swings after top-offs.
- These are pick-and-chase planktivores, so feed small foods often: live or frozen copepods, baby mysis, enriched brine, finely chopped shrimp, and tiny pellets once it recognizes them.
- They spook easily and will launch - tight lid and covered overflows are non-negotiable, and give them dim-to-medium lighting so they do not hug the glass all day.
- Skip aggressive tankmates (dottybacks, big wrasses, triggers) and fast food thieves (most anthias) - they do best with other calm, midwater fish that will not body-check them at feeding time.
- Sand matters: fine sand lets them rest and feel secure; coarse gravel tends to keep them stressed and you will see more glass-surfing and nose rubs.
- Watch for mouth damage and fin fraying from panic dashes, plus skinny-belly syndrome from being outcompeted at meals; if it is not rounding out, increase feeding frequency and target-feed with a pipette.
Compatibility
Good Tankmates
- Other small, peaceful schooling fish in the same vibe - stuff like other ponyfish/silversides (Leiognathidae/Atherinids). They tend to settle in better when they have a little group energy and nobody is trying to boss them around.
- Chill reef-safe planktivore types like firefish (Nemateleotris) and small assessors. They are calm, not bitey, and they do not compete too hard at feeding time if you spread food out.
- Peaceful small wrasses that are not terrors - think flasher/fairy wrasses (Paracheilinus/Cirrhilabrus). Active but usually not mean, and they leave ponyfish alone in my experience as long as the tank is not cramped.
- Smaller, mild gobies and blennies (watchman gobies, clown gobies, tailspot blenny). They hang in their own lane and do not harass midwater fish.
- Cardinalfish (Banggai and similar) and other calm, midwater hoverers. Good match because they are not fast bullies at the dinner bell, and they do not nip.
- Peaceful bottom dwellers and clean-up buddies - sand-sifting gobies with a gentle temperament, plus shrimp/snails/urchins. Ponyfish are typically too laid back to bother inverts.
Avoid
- Anything nippy or pushy like dottybacks and most damselfish. Even if they cannot eat a ponyfish, they will hassle them nonstop and the ponyfish just stop coming out to feed.
- Aggressive or territorial predators like larger wrasses (many Thalassoma), triggers, and most puffers. They either turn the tank into a stress fest or eventually decide the ponyfish looks snack-sized.
- Big, boisterous angels and tangs in smaller tanks. Not because they are direct predators, but they are feeding-time bulldozers and the ponyfish end up getting outcompeted and staying skinny.
- Ambush predators like lizardfish, groupers, frogfish, and big lionfish. If it can fit in their mouth, it is on the menu - ponyfish are basically built like bite-sized sardines.
Where they come from
Mekran ponyfish (Deveximentum mekranense) are little coastal marine fish from the northern Indian Ocean region, around the Mekran coast (think Pakistan/Iran shoreline). They are part of the ponyfish family (Leiognathidae) - small, silvery, schooling fish that spend their lives over sandy flats and turbid inshore water.
The vibe is very much "shallow bay baitfish". That background explains almost everything about how they act in an aquarium: they want space, they spook easily, and they do best in groups.
This is an expert-level fish mostly because of shipping stress, feeding transitions, and how touchy they can be in small, ultra-clean reef-style tanks. If you have never kept nervous schooling coastal fish, plan on a learning curve.
Setting up their tank
Give them a long tank, not a tall one. They are constant cruisers, and they calm down a lot when they can school and do laps without hitting glass every two seconds.
- Tank size: I would not bother under 75 gallons for a small group, and 125+ is where they start acting natural.
- Group size: 6+ is the sweet spot. Singles and pairs stay jumpy and hidey (or just pace).
- Layout: open swimming room with a few low rock piles or rubble zones, and big patches of sand.
- Substrate: sand helps them feel at home. Fine to medium grain is good.
- Flow: moderate, not a blender. Think tidal bay, not SPS reef surge.
- Lighting: not crazy bright. If your lights are strong, use floating cover or keep rockwork low to create dim lanes.
They jump. Like, suddenly. Use a tight lid or mesh top with no gaps around plumbing. Most ponyfish losses I hear about are "found on the floor" losses.
Filtration needs to handle frequent feeding. I like a big skimmer and aggressive mechanical filtration you actually change. These fish are planktivore/zooplankton pickers, so you will be feeding small foods often and the tank will feel "dirty" if your export is weak.
If you are running a super "polished" reef tank with near-zero nutrients, ponyfish can struggle. A little measurable nitrate and phosphate is your friend here, mostly because it keeps microfoods and pods around and lets you feed heavier without the tank swinging wildly.
What to feed them
They are small-mouthed, midwater pickers. Newly imported fish often ignore big chunks of frozen and will only take tiny moving foods at first. Once they settle, they can be great eaters, but you have to get them over the hump.
- Best starters: live baby brine (enriched), live copepods, live blackworms (rinsed well, offered in a dish), small live mysis if you can get it.
- Frozen staples: PE calanus, cyclops, finely chopped mysis, fish eggs/roe, enriched brine, small krill dust (not whole krill).
- Prepared: some will learn small pellets (0.5-1 mm) or tiny marine flakes, but do not count on it early on.
- Feeding rhythm: 2-4 small feedings a day beats one big dump. They graze in nature.
Use a feeding ring or a gentle "food cloud" in the current. Ponyfish often feed best when food drifts past them naturally. If you blast food straight at them with a turkey baster, they spook and the bold tankmates steal everything.
Watch their bellies. A healthy ponyfish has a slightly rounded look after meals, not pinched. If they stay thin, step back and simplify: reduce competition, offer smaller foods, and feed more often for a week.
How they behave and who they get along with
They are peaceful schoolers, but they are not "community" fish in the way clownfish are. Their main defense is to spook and bolt. If you keep them with the wrong neighbors, they spend their whole life stressed, hiding, or slamming into the lid.
- Good tankmates: calm sand-flat fish (small gobies, peaceful blennies), non-aggressive wrasses (think smaller Halichoeres with caution), pipefish-type setups if conditions match, and other gentle schooling fish.
- Be careful with: fast, pushy feeders (chromis can be jerks at feeding time), dottybacks, larger wrasses, and anything that "rushes" the water column.
- Avoid: predators (groupers, larger snappers, lionfish), aggressive damsels, triggerfish, and big territorial angels. Also avoid stinging-heavy reef tanks where they have to dodge coral every turn.
If you see them schooling tightly in a corner all day, that is usually fear, not happiness. A relaxed group spreads out and cruises, then tightens up briefly when startled.
They can be a little glass-surf-y for the first week or two. Dimming the lights, giving them a bigger group, and keeping hands out of the tank goes a long way. Sudden room movement (kids, dogs, doors) can set them off, so think about tank placement.
Breeding tips
I have not seen reliable home breeding reports for Mekran ponyfish specifically, and most ponyfish in the hobby are not being captive-bred. They are egg scatterers with pelagic larvae, so even if you get spawning, raising the young is the real project.
- If you want to try anyway: keep a larger group, feed heavy with small live/frozen foods, and watch for evening spawning behavior.
- You would need: a way to collect eggs (overflow/egg collector), a separate larval system, and a steady supply of rotifers and copepod nauplii.
- Expectations: plan for lots of attempts and very low early success until you dial in first foods and water quality for larvae.
Most "breeding" activity people think they see is just schooling and chasing during feeding. Real spawning tends to be quick and easy to miss.
Common problems to watch for
Most losses happen in the first month, and it usually boils down to stress plus not eating well. They can look fine one day and crash fast if they arrive beat up from shipping.
- Refusing food: very common at first. Fix by offering smaller, moving foods and lowering competition at feeding time.
- Jumping and impact injuries: watch for scraped noses and torn fins from panic runs. Lid the tank and keep the environment calm.
- Skin/fin infections after shipping: frayed fins, cloudy patches, red sores. Quarantine helps a lot here.
- Parasites: flukes and intestinal issues are worth suspecting if they eat but stay thin or flash/scratch.
- Ammonia sensitivity: they do not handle a "new tank" well, especially with heavy feeding.
If you quarantine them (you should), give the QT a big, seasoned biofilter and cover three sides of the tank. Bare glass QTs with bright light make ponyfish freak out and burn energy they do not have.
One more thing: keep an eye on oxygen. Warm marine water plus lots of small feedings can drop O2 at night. I run extra surface agitation and do not skimp on gas exchange with these fish. They look "fine" right up until they are not.
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