Indian ponyfish

Where they come from

Indian ponyfish (Deveximentum indicium) show up around India and nearby coasts where rivers meet the sea. Think silty estuaries, mangroves, and tidal flats - water that swings from nearly fresh to pretty salty depending on rain and tides.

They are one of those fish that look plain in a bucket, then under good lighting you notice the subtle silvery sheen and that weird little protrusible mouth they use to vacuum tiny food.

Setting up their tank

This is an advanced one mostly because they do not love beginner-level stability. They are schooling fish from moving, turbid water, and they stress out fast if the tank is small, bright, or inconsistent.

• Tank size: I would not bother under 40-55 gallons for a group. Bigger feels easier because the salinity and temperature swings are slower.
• Group size: 6+ is where they settle in. Singles or pairs stay jumpy.
• Salinity: true brackish. I have had the best long-term luck around SG 1.005-1.012 (roughly 7-16 ppt), and I keep it steady rather than chasing "tides" in a home tank.
• Temp: mid-70s to low-80s F (24-28 C).
• Filtration: strong and mature. They are constant pickers and produce more waste than you would guess for their size.
• Flow and oxygen: moderate flow plus good surface agitation. Estuary fish like oxygenated water even if it looks muddy in nature.
• Substrate: sand is your friend. They spend time near the bottom and sand is easier on them than sharp gravel.
• Decor: open swimming space with some cover (mangrove-style roots, driftwood, rock piles). They like somewhere to tuck in when spooked.
• Lighting: not too intense. Floating plants (if your salinity allows) or dimmer lighting keeps them calmer.
• Lid: tight. They can jump when startled.

Acclimation matters with these. If they come from lower salinity, raise it slowly over days, not hours. Drip acclimation is good, but the real trick is not rushing the move to your target SG.

What to feed them

They are micro-predators. That little mouth shoots out and they pick tiny crustaceans, worms, and zooplankton. If you offer only big pellets, they will act interested and then slowly lose weight.

• My go-to staples: frozen mysis (small), brine shrimp (better enriched), finely chopped krill, copepods, and small sinking micro-pellets once they recognize them as food.
• Live foods that flip the switch: live baby brine, live blackworms (rinse well), cultured copepods, and small amphipods.
• How to feed: small amounts 2-3 times a day at first. They do better with frequent small meals than one big dump.
• Target feeding: broadcast into the flow so it drifts like plankton. They will chase and peck midwater if food moves naturally.

How they behave and who they get along with

They are peaceful, schooling, and honestly kind of nervous. Sudden movement outside the tank, heavy-handed maintenance, or aggressive tankmates will keep them in "flight mode" and they will stop feeding well.

• Best tankmates: other calm brackish fish that like similar salinity (some gobies, bumblebee gobies at the right SG, knight gobies if the tank is big, archerfish only if you know what you are doing and the ponyfish are not being bullied).
• Avoid: fin nippers, fast boisterous eaters, puffers, large monos/scats unless the tank is very large and you can feed in a way the ponyfish still get their share.
• Intraspecies: they do best in a group. Expect tight schooling when they are new, then looser cruising once they feel safe.

Breeding tips

Breeding ponyfish in home aquariums is not common. They have some unusual reproductive biology in the family (ponyfish are famous for it), and most hobbyists never see viable spawns, let alone raise fry.

If you want to take a swing at it anyway, your best bet is a big, calm, mature brackish tank with a well-fed group and very stable salinity. If you ever see tiny fry, they are going to need microscopic foods right away (rotifers/copepod nauplii) and very clean, very stable water. Most people lose them at the first-food stage.

Common problems to watch for

Most issues I have seen with Indian ponyfish come down to stress, starvation-by-competition, and swinging brackish parameters.

• Not eating or "spitting" food: food is too large, too dry, or they are stressed. Switch to smaller frozen/live foods and dim the tank a bit.
• Slow weight loss: they are not getting enough. Feed smaller foods more often, and make sure tankmates are not vacuuming everything first.
• Ich/white spot after purchase: very common with wild-caught brackish fish. Quarantine helps a lot. Treatment choice depends on salinity and the meds you use - read carefully because some meds behave differently in brackish water.
• Gill stress and hanging at the surface: check ammonia/nitrite first, then oxygen/flow. Estuary fish still hate low oxygen.
• Sudden deaths after "topping off": topping off with salty water instead of fresh makes salinity creep up fast. Mark your tank and use a refractometer so you are not guessing.
• Jumping: usually a scare response. Tight lid, cover gaps, and avoid loud slams during feeding/maintenance.