How to Maintain a Stable Sulawesi Shrimp Tank

Your Sulawesi tank is running, the shrimp are grazing, and now the job is keeping it that way. Most of that job is what you don’t change: top off with pure water, change a little at a time with matched water, keep waste out of a warm tank, and measure before you correct anything. The water sits in a warm, alkaline band that holds less oxygen and forgives less waste than a Neocaridina tank does. So the routine that keeps a colony going is small, matched and slow.

How far a Sulawesi tank’s readings can move before it stops being stable

Only slowly, and only inside the group band. Stable means your readings stay in range and barely move from week to week, not that they hit one exact number. Two tanks can both sit at legal values and only one of them be stable. A tank that reads pH 7.6 every week is fine. A tank that reads pH 7.6 one week and pH 8.3 the next isn’t, even though neither reading is outside the range.

These are typical ranges for the group, not survival limits and not a promise. A particular species or line may sit in a narrower part of the band. Where a seller publishes a narrower range for a named line, that line’s record is what applies to it.

Why is the band drawn where it is? Because of the lakes these shrimp evolved in. Published Lake Towuti water parameters put the lake at approximately 82°F (28°C) throughout the year, with only weak thermal stratification in the water column.¹ Lake Matano has been studied partly because it combines abundant iron oxides with minimal seasonal temperature variability.² Neither of those is a target you set on a heater. What they describe is a place where the numbers barely move. That’s the part most home tanks fail to copy, even when every reading is correct.

Of the readings in the table, KH is the one that protects the others. Alkalinity is the water’s capacity to neutralize acids and so hold a fairly stable pH. Water carrying more of it shifts less when something acidic enters.³ Let KH slide toward the bottom of the band and pH becomes the reading that moves first. That matters, because pH also decides how dangerous the waste in your tank is. So watching KH gives you an early warning for two problems at once.

Before you change anything else, write down where your tank actually sits inside the band this week, and keep writing it down. A single reading tells you almost nothing. A column of readings tells you whether you have a stable tank, a slow drift or a fault.

Top off evaporation with pure RO water, not remineralized water

Use pure RO or DI water, because what evaporates from a warm Sulawesi tank is pure water and the minerals stay behind. Evaporation removes water and leaves the dissolved solids behind, concentrating them in what remains.⁴ That’s plain physics, and it’s the whole reason a Sulawesi tank’s TDS and GH climb on their own while you’re doing nothing wrong.

So replace the volume evaporation takes with pure RO or DI water and nothing else. Top off with remineralized water and you’re adding minerals to water that already holds more than it started with, so every top-off makes the next reading worse. Left alone, that’s enough to walk a tank out of the top of the TDS and GH band without a single dramatic event to blame.

In practice, top off little and often, instead of letting the level fall and then refilling. A float valve or a small auto top-off unit keeps the water line flat. It also takes over the one maintenance job that’s easiest to skip. If you top off by hand, do it on a fixed schedule, not when the tank looks low.

How do you know your top-off routine is working? Watch TDS, not the water line. A TDS reading that climbs steadily between water changes means minerals are getting in somewhere, and top-off water is the first place to look.

How big a water change a Sulawesi colony can take

A small one, made with matched water and repeated if needed, because a water change on a Sulawesi tank isn’t a cleaning step. It’s a controlled replacement of water, meant to move a reading back where you want it while disturbing everything else as little as possible. That framing decides the size, the timing and the speed.

Match the replacement water before any of it reaches the tank

Mix and rest the replacement water in a separate container, then test its temperature, pH, GH, KH and TDS against the tank before you use it. Water mixed straight into a bucket and poured in is the very shock you were trying to avoid. On a specialist warm alkaline tank, that shock lands on animals with little tolerance for rapid change in chemistry or temperature.

Once it matches, add it slowly. Drip or ladle it in over a long stretch. The colony meets the new water gradually, and you have time to stop if something looks wrong halfway through.

Why does precision matter more here than on a hardier tank? The molt. Crustaceans have to cast the exoskeleton to grow,⁵ and most of the calcium for the new one comes from the water the animal lives in, not from its food.⁶ So mineral content that moved while a shrimp was between molts is felt at the molt, not on the day of the change. That delay is why a colony can look untroubled for weeks and then run into trouble in a few days with no obvious trigger that week.

Why the ten percent water change figure on Sulawesi care sheets isn’t measured

Because nobody has measured it for these shrimp, and none of the care sheets publishing it cites a source. The Sulawesi care sheets that rank for this question all publish some version of about ten percent every one to two weeks. It’s a reasonable habit to start from. Treat it as a default, not as a schedule your tank owes you.

Your own readings are the better instruction. If TDS, GH and KH are where you want them and nitrate is comfortably under 10 ppm, a water change is routine. It can be small and unhurried. If a reading has drifted, size the change to move that reading back over more than one session. Several small changes get you to the same place as one large one, without asking the colony to absorb the whole difference at once.

That’s also why large changes are worth avoiding. A single big replacement moves temperature, minerals and pH together, and it does it faster than anything in the Sulawesi shrimp natural habitat ever moves.

Why warm alkaline water punishes leftover food in a Sulawesi tank

Warm, alkaline water turns more of the ammonia from rotting food into its toxic form, so the same leftover does more harm here. Total ammonia in water is split between the ammonium ion and un-ionized ammonia, and the un-ionized form is the one that drives ammonia toxicity in aquatic animals. That split isn’t fixed. The ratio of un-ionized ammonia to ammonium in fresh water increases by tenfold for each rise of a single pH unit, and by roughly twofold for each 10 degree Celsius rise in temperature across the range EPA assessed.⁷

A Sulawesi tank sits high on both of those at once. So the same total ammonia reading isn’t the same problem here as in a Bee Caridina tank at pH 6.5. A pellet left under a rock matters more in this tank than in a cooler, softer one. The answer isn’t a special product or an extra filter. It’s less food going in and no leftovers staying in.

Your colony may want more or less than that. Species, colony size and how much grazing surface the hardscape actually carries all change the answer, and a young tank with thin biofilm isn’t a mature one. Check the rock, not the calendar. If the shrimp are grazing steadily across the hardscape and the surfaces still carry a visible film, the tank is feeding them and you can leave the food out.

What doesn’t work is using extra food to make up for a tank that isn’t mature enough. More food in a tank with too little grazing surface adds waste without adding anything to graze, and in warm alkaline water that’s a bad trade.

Hold oxygen up in a warm Sulawesi tank without adding current

Add aeration, not flow: a warm tank holds less oxygen, but your shrimp still need calm water at the rock. Cold water can hold more dissolved oxygen than warm water,⁸ so a tank running at the top of the Sulawesi temperature band starts with less oxygen than a room-temperature shrimp tank at the same level of aeration. You can’t see that gap, which is why aeration is the part of a warm tank that’s easiest to under-provide.

What you can raise is the aeration. What you shouldn’t raise with it is how hard the water moves at shrimp level. Air-driven sponge filtration and air stones are the usual answer in these tanks. The aeration and the filtration come from the same gentle source, and there’s no intake for shrimplets. Sulawesi shrimp feed by working over surfaces, and a shrimp being blown off a rock isn’t eating.

Judge the result by what the animals do. Shrimp grazing calmly on exposed rock faces in the flow are comfortable. Shrimp that stay wedged in shelter on the low-flow side, or gather high in the water column and stop grazing, are worth taking seriously. Check temperature, aeration and recent waste before you assume anything else.

Reading a bad week in a Sulawesi tank before you change anything

Measure first, because a slow drift and a sudden failure look alike from the outside and need opposite responses. Slow drift shows up in your readings before it shows up in the shrimp: TDS creeping, KH sagging, nitrate climbing week after week. A failure shows up in the shrimp first, and hard in one reading. Usually a heater, a pump or an air supply stopped, or something got into the water.

The first response to both is the same, and it isn’t a water change. Test ammonia, nitrite, temperature, pH, KH, GH and TDS. Then make an honest list of everything that changed in the last week, including new hardscape, a cleaned filter, a new food, a treated plant or anything used near the tank. A tank that has been sitting still doesn’t usually turn without a reason, so that list is where to look first.

Then resist the big corrective change, however tempting it is to pour in fresh water and feel you’ve done something. If the readings show drift, correct it across several small matched changes and let the colony arrive gradually. If they show a fault, fix the fault first and let the water settle with the tank running. Chasing a reading while the cause is still there means two disturbances instead of one.

Raising the temperature isn’t a repair

No, warming the tank won’t fix a struggling colony, and it costs you dissolved oxygen at the same time. Warmth gets treated as a general tonic in this hobby, so it’s worth closing that door. In a study on a crab, warmer water shortened the time between molts and cut the growth at each one.⁹ That’s a crab, not a Caridina, so read it as a direction only. Nothing in it supports pushing a Sulawesi tank hotter to speed a colony along.

If shrimp are dying and the readings don’t explain it, stop and get help. Don’t treat blind. Copper-bearing products and many fish medications can harm shrimp and snails, and an unneeded treatment in warm alkaline water becomes a second problem stacked on the first. A description of symptoms isn’t a diagnosis, and no article can give you one.

What the research says about Sulawesi shrimp tank maintenance

The molting and temperature points in this guide come from research on other crustaceans, not on Sulawesi Caridina, so take them as the mechanism behind the advice, not as measurements of your shrimp. The point that crustaceans must regularly cast the exoskeleton to grow comes from an FAO paper on farming freshwater prawns.⁵ The calcium point comes from Luquet’s review of biomineralization across crustaceans. It finds that the major source of the calcium used to build a new exoskeleton is exogenous, meaning the water the animal lives in. Food and stored reserves contribute less.⁶

The temperature point comes from Kuhn and Darnell’s work on the lesser blue crab. There, elevated temperature was measured to decrease both the intermolt period and the growth per molt, producing smaller sizes at each instar. The authors note that earlier laboratory and field work suggests temperature affects both in many crustaceans.⁹ None of them measured Sulawesi shrimp. What they support is the habit this guide is built on: keep the water steady and leave the heater where it is.

The weekly checks that keep a Sulawesi tank inside its band

A short, dull routine repeated without variation does almost all of the work in a stable Sulawesi tank. That’s the point of it.

• Top off to the same water line with pure RO or DI water, on a schedule.
• Read temperature, pH, KH, GH and TDS, and write them into a running log so drift shows up as a trend instead of a surprise.
• Look at the hardscape: grazing surfaces carrying film, shrimp working across them, and no food left from the last feeding.
• Confirm the heater, air supply and filter are all actually running, since these are what fail suddenly.
• Don’t vacuum the grazing surfaces clean, and don’t replace filter media and rearrange hardscape in the same week.

Water changes come out of the log, not the calendar. When the log shows a trend instead of a wobble, mix matched replacement water, change a small volume slowly, and check the following week that the trend actually turned. When the log is flat, a small change is still worth doing for the nitrate, but there’s nothing to correct and no reason to make it large. Let the log set the timing of Sulawesi shrimp water changes.

Anything you add later has to belong in this same water, because a shrimp sold under a Sulawesi name isn’t automatically kept in Sulawesi conditions. Check a new line against the table above before it goes in. Tank-bred Sulawesi shrimp belong in this water, while Bee and Crystal Caridina need soft, acidic water and shouldn’t be mixed into it.

A colony that has spent a year in water that never moved much is what this routine is built for. It isn’t exciting to run. The weeks when you measure, write it down and do nothing are the weeks doing the most work. Few hobbies count doing nothing as effort.

References

9 Sources

1. Geomicrobiological Features of Ferruginous Sediments from Lake Towuti, Indonesia, Vuillemin et al., Frontiers in Microbiology 7, article 1007, 2016.
2. The biogeochemistry of tropical lakes: A case study from Lake Matano, Indonesia, repository record and abstract, Crowe et al., Limnology and Oceanography 53(1), 2008.
3. Alkalinity and Water, U.S. Geological Survey Water Science School, updated August 24, 2026.
4. Chloride, Salinity, and Dissolved Solids, U.S. Geological Survey Water Resources Mission Area, March 1, 2019.
5. Farming freshwater prawns, biology chapter, Food and Agriculture Organization of the United Nations, FAO Fisheries Technical Papers No. T428.
6. Biomineralizations: insights and prospects from crustaceans, Gilles Luquet, ZooKeys 176, 103-121, 2012.
7. Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater (2013), U.S. Environmental Protection Agency, Office of Water, April 2013.
8. Dissolved Oxygen and Water, U.S. Geological Survey Water Science School, updated August 24, 2026.
9. Elevated temperature induces a decrease in intermolt period and growth per molt in the lesser blue crab Callinectes similis Williams, 1966, abstract, Kuhn and Darnell, Journal of Crustacean Biology 39(1), 22-27, January 2019.