Sulawesi Shrimp Staying on the Bottom: What to Check First

Your Sulawesi shrimp has been parked on the bottom for an hour, and you can’t tell whether it’s grazing or in trouble. It’s fine as long as something on it is still moving: a grazing shrimp works its mouthparts nonstop, sweeps its antennae and fans its swimmerets, even when it hasn’t crossed the rock in ten minutes. A shrimp that’s truly motionless, legs tucked or splayed and antennae flat, is telling you the water changed. Check temperature, ammonia and oxygen first, in that order, and don’t fix anything until you have a reading.

How to tell a grazing Sulawesi shrimp from one that has stopped moving

Get level with the glass and watch one animal for a full minute. You’re not looking for travel. Sulawesi shrimp will park on one patch of rock and work it, so a shrimp that hasn’t moved its body an inch may be perfectly busy. What you’re looking for are three smaller movements: the mouthparts scraping in a fast, almost mechanical rhythm, the antennae flicking and sweeping the water, and the swimmerets under the abdomen beating steadily.

All three running means the animal is busy. All three stopped, or slowed to the odd twitch, and the safe move is to treat it as a tank problem until your readings say otherwise. That’s the line we’d draw at Shrimp Aquatics. It matters because the two states look identical in a photo, which is why posting a picture and asking the internet to judge it rarely gets you anywhere.

A colony that has vanished from view is a different problem from a colony sitting in the open doing nothing, and Sulawesi shrimp hiding is where that one starts. This page is about the shrimp you can see, doing nothing.

Whether one Sulawesi shrimp is down or the whole colony decides where you start

How many animals are actually affected? Count them before you touch anything. It’s the cheapest bit of diagnosis you’ll do all day, and it splits the problem cleanly in two.

One shrimp on the floor while the rest graze normally is almost never a water fault, because water reaches every animal in the tank at once. A single shrimp is far more likely to be mid-molt, freshly molted and soft, old, or injured. That branch is further down this page.

Several animals down at once, or a colony that went quiet over a few hours, points at something that reached all of them together: temperature, dissolved gases, ammonia, or whatever you last added to the tank. Work the water first, and leave the individual animals alone while you do.

Test your Sulawesi tank before you change anything, because warm alkaline water makes the same ammonia reading worse

Take readings before you do a water change. We know you want to pour in fresh water and be done with it. But a change made now wipes out the evidence and lands a second insult on top of the first, while ten minutes with a test kit costs you nothing.

1. Temperature, with a thermometer you trust. Not the dial on the heater. A stuck heater or a cold snap can take the tank out of the range we keep to without changing a single chemical reading, so this is the one you rule out first.
2. Ammonia and nitrite. Any reading above zero on either is your answer, and in this tank a small number isn’t a small problem.
3. pH and KH. These tell you whether the buffer holding the tank up is still there, or whether it’s been quietly falling.
4. TDS. Compare it with what you last recorded, not with a target. The direction it’s moving in is the useful part.

Why 0.25 ppm of ammonia is not the same number in a Sulawesi tank

Total ammonia in water sits in two forms, the ammonium ion and un-ionized ammonia, and the un-ionized form is the one that drives toxicity in aquatic animals. Which way the balance tips depends on pH and temperature. The ratio of un-ionized ammonia to ammonium rises about tenfold for every single pH unit, and roughly twofold for every 10 degrees Celsius of warming across the range these tanks sit in.¹ Put those together and a Sulawesi tank at pH 7.5-8.5 and 79-86°F (26-30°C) holds a far larger share of its total as toxic ammonia than a soft, cool bee tank showing the identical test result.

That’s the honest reason these shrimp have a reputation for sudden collapses. Nothing exotic happens. The same waste a cherry tank soaks up becomes a real dose here. A colony that lies down together after a heavy feed, or after something died behind the rock, is usually reacting to exactly that.

How low oxygen in a warm tank shows up as shrimp that stop moving

Cold water can hold more dissolved oxygen than warm water, so oxygen falls as temperature rises.² A tank kept at the top of 79-86°F (26-30°C) already has less headroom than a room-temperature tank, and anything that adds demand eats into what’s left: a bloom, a warm night, a filter that slowed down. Does less oxygen actually mean a quieter shrimp? In farmed Pacific white shrimp, the sound of shrimp activity rose and fell with dissolved oxygen.³ It’s a pointer to the direction of travel, not a measurement of your colony.

So look at the surface. A still, oily film across the top is worth breaking up before you touch anything else in the tank. Adding air is safer than adding flow, and how much surface renewal a warm tank really needs is covered in Sulawesi shrimp oxygen requirements.

Treat a reading outside those figures as a lead, not a verdict. A tank that has sat a little under the bottom of that pH band for a year is a different case from one that dropped half a point last Tuesday. It’s the movement that puts shrimp on the floor, not the number on its own.

When your Sulawesi water tests clean, look at what changed in the last week

A clean set of readings isn’t an all clear. It means whatever hit the colony has already passed through the water, or never showed up on a hobby test kit at all. So what did you do to this tank in the last seven days? Write down everything you added, replaced, cleaned or adjusted.

A mineral batch that was not finished before it went in

This one catches careful keepers, because they did the work and still got caught out. The two common Sulawesi salts behave completely differently. Sulawesi Mineral 7.5 almost totally dissolves within seconds, and the water is ready to use immediately.⁴ Sulawesi Mineral 8.5 doesn’t. Its maker says it will almost totally dissolve if CO2 is added over roughly 3-4 days at about one bubble per second, and that you then have to aerate the water with an air stone for at least three hours to drive the CO2 off before you use it.⁵

Skip either half of that and you’re pouring in water still loaded with carbon dioxide and still carrying undissolved salt, which is exactly the state the maker tells you to clear before use. If the colony came down within an hour or two of new water going in, start with the batch, not the tank. If you switched salts, changed brands or mixed in a hurry, start there too. Replacement water gets mixed, dissolved, degassed and tested outside the tank, and that’s what remineralizing RO water for Sulawesi shrimp walks you through.

Topping off with the wrong water, a little at a time

Evaporation concentrates dissolved solids in the water left behind.⁶ Water leaves as vapor and minerals don’t, so the tank climbs. Top off with your remineralized mix instead of plain RO and you’re adding a second load of minerals on top of the ones that never left. That’s how a tank creeps upward over a couple of months without anyone doing anything wrong on any single day. Shrimp cope with the drift until a molt, and then they don’t.

Something that came in on your hands or in a bottle

Copper is worth naming because it turns up in plant fertilizers, snail treatments, fish medications and old plumbing. Elevated copper is toxic in aquatic environments and can harm invertebrates, and how much harm a given amount does depends on water characteristics including pH, alkalinity, dissolved organic carbon and hardness.⁷ Did a whole colony go down within hours of a treatment, a new decoration, a fertilizer dose or a hand with soap or lotion on it? That timing is your evidence. No test kit is going to confirm it for you.

Why is one Sulawesi shrimp lying on its side while the rest graze?

Usually because it’s molting, so start there. All crustaceans have to cast the exoskeleton regularly to grow.⁸ A shrimp that’s just come out of her shell is soft, pale and slow, and lying still in a crevice is exactly what she should be doing. Leave her alone. Don’t net her, don’t move her, and don’t feed the tank heavily to cheer her up.

Look on the substrate for the cast shell. An intact empty shell nearby is the best news on this page. If the old shell has split at the neck and the shrimp can’t push free of it, you’re looking at a failed molt, not a tank fault, and pulling at it by hand isn’t a rescue.

Molt trouble sends you back to the water anyway, because crustaceans take most of the calcium for a new shell from the water they live in.⁹ So a colony whose GH and KH have been sliding is a colony that’ll start failing molts, and the first sign is often one shrimp stuck half out of a shell, long before anything tank-wide.

One more check before you settle on a molt. Look at the tail muscle against the light. Faded color is common and usually reversible. A chalky, opaque white block of muscle running through the abdomen is a different thing: in a farmed freshwater prawn, lethargy with opaque abdominal muscle is a recorded sign of white tail disease.¹⁰ That’s not a diagnosis of your shrimp. We mention it because opaque muscle plus a motionless animal is the combination that should move you from troubleshooting to isolating the animal and asking for qualified help.

One honest limitation, stated plainly. No study we could find measures lethargy, posture or recovery in any Sulawesi lake Caridina. Everything above is mechanism drawn from wider crustacean and water chemistry work, applied to the conditions these shrimp are kept in. That’s enough to tell you what to test. It isn’t enough to tell you what one shrimp’s odds are.

Correct a Sulawesi tank slowly, because the correction is what usually kills the colony

You have a reading and a probable cause. Now do less than you want to.

• Get air into the water first. An air stone or a raised outlet costs nothing, helps in almost every scenario on this page, and can’t shock anything.
• Stop feeding prepared food until the animals are grazing again. A mature tank already has grazing surfaces they can use, and uneaten food here costs you more than it gives.
• Lift anything uneaten, and anything dead, before you do anything else. In water this warm, a body behind the rock is an ammonia source with a clock on it.
• Bring Sulawesi tank temperature back inside 79-86°F (26-30°C) gradually, and let the heater do it instead of adding hot water.
• Don’t do a large water change to reset the tank. A big unmatched change is a second shock landing on animals that haven’t absorbed the first.
• Don’t dose anything at a colony you haven’t diagnosed. Medications, buffers and pH adjusters are how a recoverable tank becomes a finished one.
• Don’t chase a number back to the middle of a range. In this group, steady beats correct every time.

If a water change really is justified, keep it small. Mix and test the replacement outside the tank, match the temperature closely, and add it slowly over an hour or more, not in one pour. The usual rule is to let the tank drift back to its old numbers over days, not to hit them this afternoon.

When a motionless Sulawesi colony needs qualified help, not another water change

Most keepers keep testing and adjusting too long while the colony thins out. Stop and get a second opinion if you see any of these. Opaque white muscle in more than one animal. Deaths that carry on for more than a few days after the water has read clean and stable. A colony that won’t go back to grazing once temperature, ammonia and oxygen are all where they should be. The other warning signs of a failing colony are listed in common health problems in Sulawesi shrimp.

At that point the useful next step is a qualified aquatic veterinarian or an experienced local specialist who can look at the animals, not another round of test strips. Bring your numbers, including the ones from before you corrected anything. That record is worth more than any photo.

What the research says about Sulawesi shrimp staying on the bottom

None of the work below is on Sulawesi shrimp, so use it to decide what to check, not to judge how your shrimp will do. The oxygen link comes from farmed Pacific white shrimp monitored acoustically in production ponds, where shrimp-associated sound tracked dissolved oxygen in the same direction as it rose and fell.³ Those are marine penaeids in a pond, not lake Caridina in a tank.

The molting notes come from the farmed freshwater prawn and from crustaceans in general. In that prawn, mating only takes place between hard-shelled males and ripe females that have just completed the pre-mating molt and are therefore soft-shelled.⁸ Across crustaceans, the major source of calcium for the new exoskeleton is exogenous, meaning the surrounding water, while stored reserves and food contribute less.⁹

The opaque muscle warning comes from white tail disease in Macrobrachium rosenbergii, where lethargy and opaque abdominal muscle are recorded clinical signs and mortality reaches up to 100 per cent within four days.¹⁰ That’s a different species under culture conditions, which is why this page treats it as a reason to isolate the animal and ask for help, not as a diagnosis.

References

10 Sources

1. Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater, U.S. Environmental Protection Agency, Office of Water, April 2013.
2. Dissolved Oxygen and Water, U.S. Geological Survey, Water Science School, page updated August 24, 2026.
3. Linking Dissolved Oxygen Fluctuations to Acoustic Activity in the Litopenaeus vannamei Under Operational Pond Conditions, Journal of Marine Science and Engineering 14, article 682, 2026.
4. Sulawesi Mineral 7,5, Minerals and trace elements, SaltyShrimp, manufacturer product information page.
5. Sulawesi Mineral 8,5, Minerals and trace elements, SaltyShrimp, manufacturer product information page.
6. Chloride, Salinity, and Dissolved Solids, U.S. Geological Survey, Water Resources Mission Area, March 1, 2019.
7. Supplementary Training Materials for Aquatic Life Criteria, Copper, Background, U.S. Environmental Protection Agency, Office of Water, page updated May 6, 2026.
8. Farming freshwater prawns, biology chapter, Food and Agriculture Organization of the United Nations, FAO Fisheries Technical Paper 428.
9. Biomineralizations: insights and prospects from crustaceans, Gilles Luquet, ZooKeys 176, 2012.
10. White Tail Disease of Freshwater Prawn, Macrobrachium rosenbergii, abstract, Indian Journal of Virology 23, 2012.