Spotted scat

Where they come from

Spotted scats are classic “mangrove edge” fish. You find them around estuaries, river mouths, and brackish lagoons across Southeast Asia and northern Australia—places where the water swings between fresh-ish and salty depending on tides and seasons.

That back-and-forth lifestyle explains a lot about them in the aquarium: they’re tough, hungry, messy… and they really appreciate you treating brackish water like a real thing, not an afterthought.

Setting up their tank

The biggest mistake I see is people buying cute little scats and putting them in a “medium community tank.” They grow fast, turn into chunky dinner plates, and they do it while producing a ridiculous amount of waste.

• Tank size: I wouldn’t start with less than 75 gallons for a small group, and 125+ is where it starts feeling comfortable long-term.
• Group size: They’re less skittish in a group (3–6 works well). Solo scats can get weirdly pushy or nervous.
• Filtration: Go bigger than you think. Strong canister or sump-style turnover, plus lots of mechanical media you can rinse often.
• Flow/oxygen: They like well-oxygenated water. A powerhead or strong return helps a lot.
• Decor: Open swimming room with some driftwood/rocks for breaks. Mangrove-style roots look awesome, just leave space.
• Substrate: Sand or smooth gravel. They sift and graze; sharp stuff is asking for trouble.

Salinity depends on how you want to run them, but I’ve had the best luck keeping them solidly brackish and stable. A common sweet spot is around SG 1.005–1.012, with many keepers gradually going higher as they mature (some adults do great close to marine). The real key is: pick a number and stop bouncing it around.

What to feed them

Scats are basically hungry garbage disposals with fins—in a good way. They’re omnivores that love plant matter, but they also go nuts for meaty foods. If you only feed protein, they can get chunky and the tank will get gross fast.

• Staples: quality pellets/flakes that include algae/spirulina (they actually eat it).
• Veggies: blanched zucchini, spinach, shelled peas, cucumber slices. Clip them so they don’t float away.
• Meaty treats: mysis, krill, chopped shrimp, clam. Not every meal, but great for variety.
• Grazing foods: nori sheets (seaweed) are a huge hit in brackish setups.

How they behave and who they get along with

They’re active, curious fish that spend the day cruising and picking at stuff. In a group they’re way more confident, and you’ll see a lot of “follow the leader” swimming.

Temperament-wise, they’re not usually pure bullies, but they’re strong, fast, and food-obsessed. Anything small enough to fit in their mouth—or slow enough to get outcompeted—is going to have a bad time.

• Good tankmates: monos (Monodactylus), archerfish (in big tanks), larger brackish gobies, knight gobies (with care), big mollies in brackish, some puffers only if you’re experienced and the tank is large.
• Avoid: tiny community fish, delicate long-finned fish, and anything you can’t feed well in salty water.
• Inverts/plants: most “freshwater” plants and shrimp/snails won’t last as salinity climbs. Expect scats to snack on what they can catch anyway.

Breeding tips (realistic expectations)

Breeding spotted scats at home is pretty rare. In the wild they migrate and spawn under conditions that are hard to copy in a glass box. Most fish in the trade are wild-caught or farm-raised with large-scale setups.

If you ever wanted to take a swing at it, you’d be looking at a big group, a very large system, and gradually shifting salinity/seasonal cues. But for most of us, scats are a “display fish” project, not a breeding project.

Common problems to watch for

Most scat problems trace back to two things: dirty water (because they’re messy) and unstable salinity (because people top off or water-change without checking). Get those under control and they’re pretty forgiving.

• Nitrate creep and cloudy water: they eat a lot and poop a lot. Bigger filter, more water changes, and less overfeeding fixes most of it.
• Ich/white spot after purchase: common with wild-caught fish and shipping stress. Stable temp, good oxygen, and treating in brackish correctly (many meds have limits with salt—read labels).
• Fin damage from nets/spines: use a tub/container to move them and keep décor snag-free.
• “Won’t eat” new fish: usually stress. Dim lights, offer nori/spirulina foods, and give them time. Once they start, they rarely stop.
• Sudden swings in salinity: topping off with salty water is a classic mistake. Evaporation leaves salt behind, so top off with fresh water, and only add salt when you’re doing water changes.