What is the water actually like in the lakes your Sulawesi shrimp come from? It’s warm all year, mildly alkaline and very low in dissolved minerals, a pairing most fresh water doesn’t manage, and it’s slow to change. These shrimp come from a handful of ancient lakes on one Indonesian island. The deep water there barely moves, and in the deepest lake its layering has held for decades. That steadiness is the part of the lake your tank can copy most closely, and it matters more than matching any single lake reading.

Sulawesi lake water is warm, mildly alkaline and very dilute

These lakes pair alkaline water with very little dissolved material, which most alkaline fresh water doesn’t do. It’s usually mineral rich as well. Here the lakes sit in catchments of ophiolitic rock and weathered lateritic soils, which deliver iron in quantity and almost no sulfate. So the water reads alkaline on a pH pen while carrying very little in it.

Matano and Towuti, the two Malili lakes with the most published chemistry, are best read one study at a time, because the papers don’t always agree. Two studies of Lake Towuti put its pH a little differently, though both describe a dilute lake close to neutral.¹² Before you treat any one figure as fixed, check it against the full readings for Lake Matano water parameters and Lake Towuti water parameters.

Lake Poso sits apart from the other two. It’s 485 m above sea level, covers 364 km² and reaches around 400 m deep, with a mean annual temperature of about 77 to 79°F (25 to 26°C). It’s an oligotrophic lake where phosphorus is the limiting nutrient. Surface concentrations sit at or below 0.01 micromolar dissolved phosphorus and 13 micromolar dissolved nitrogen, and oxygen falls to zero near 90 m.³

You’ll notice we don’t give a pH for Lake Poso, and that’s on purpose. The 2024 study above works at a surface pH near 7. A watershed survey published readings running from 9.15 to 10.21, across sampling zones that take in rivers and estuaries as well as the lake.⁴ Those two pictures can’t both describe the water a shrimp sits in. Averaging them would hand you a tidy number nobody has measured.

None of these are tank targets. Reading a lake and working out which water to mix are two different jobs. If the second one is why you’re here, start from which lake your Sulawesi shrimp come from and take the tank numbers from there.

What keeps Sulawesi lake water alkaline when it’s this soft?

Bicarbonate. In Lake Towuti the little that’s dissolved is dominated by magnesium and bicarbonate.¹ Lake Poso gets there from different rock. It’s a soft water lake where calcium far outweighs magnesium and bicarbonate far outweighs sulfate and chloride, mainly because heavy rain weathers calcareous and siliceous metamorphic bedrock.⁵

That bicarbonate is the detail worth carrying home. In most fresh water, hardness and buffering both come from calcium carbonate, so soft normally means unbuffered and acidic. Not here. The dissolved load stays low while there’s still carbonate in the water holding the pH up. For your tank, that means carbonate hardness has to be there even while the total mineral content stays low, and that’s the pairing the range at the end of this page is built around.

The iron the Malili catchments shed has a second effect. It scavenges phosphorus, so production in the open water is expected to be limited,¹ and what the shrimp graze grows as a film on hard surfaces instead.

How light and oxygen change with depth in a Sulawesi lake

Both run out, and the oxygen runs out early. In all three lakes the water holds no oxygen below somewhere between about 90 and 130 m,⁶¹³ so nothing that needs dissolved oxygen can live down there. What looks like an enormous body of water is, for a grazing invertebrate, a thin rim around the edge.

The top of that rim is squeezed too. A grazing film only grows where light reaches the bottom, and that pins the shrimp to the shallows. Shallow tropical water is warm water, and warmth costs oxygen: cold water holds more dissolved oxygen than warm water does.⁷ So the band these animals live in is shallow, bright and wave washed, and in oxygen terms it’s already working near the top of what warm water can carry.

Inside that rim the shrimp sort themselves by depth and by surface, from gravel in the shallows to boulders a few meters down.⁸ That layout of the Sulawesi shrimp natural habitat is what your hardscape copies.

What this means for your tank

A Sulawesi tank is a warm tank, so it starts with less oxygen in it than a cool one. That’s why keepers who do well with these shrimp treat aeration as part of the build, not something to bolt on later. It’s also why crowding and poor circulation bite harder here than they do in a cherry shrimp tank.

How steady is Sulawesi lake water through the year?

Very steady at depth, and seasonal near the surface. Lake Matano is layered by weak temperature and salt gradients that persist over seasons, decades and possibly centuries, and its deep water never mixes. That deep water is estimated to renew itself only over several hundred years.⁹

Lake Towuti is layered too. Its bottom water holds a nearly constant temperature, while roughly the top 90 m varies with the seasons, running cooler and mixing more in the dry season from July to September.² So the shallows the shrimp live in are the part of the lake that does move, and they move with the seasons.

Quick changes along a shoreline come from the land. Around Soroako on Lake Matano, runoff and siltation events tied to decades of nickel mining, logging, farming and town growth keep resetting the diatom community on the lake bed to an earlier successional stage,¹⁰ one of several threats now pressing on Sulawesi lake ecosystems.

Your tank doesn’t get seasons, but it does get the room it sits in, a heater that sticks or a water change mixed in a hurry. Shrimp that evolved in water this steady never had to survive a sudden swing, and the long history behind that is much of why Sulawesi lakes are unique.

Which parts of the Sulawesi lake environment are worth copying at home

Copy the steadiness, the water chemistry and the grazing surfaces, and leave the lake readings and the scale behind. You can’t reproduce a 600 m lake, and you don’t need to. So which parts actually carry the shrimp, and which are just scenery?

Warmth that doesn’t move. The Towuti catchment sits under an annual average air temperature of 26°C, and a tank that holds one steady reading beats a tank that wanders through a wider band.
Alkaline water that’s still low in dissolved minerals. That pairing is the real signature of the habitat, and it’s why we’d build the water from RO plus a Sulawesi mineral, not a hard water salt.
Hard, inert rock for a Sulawesi tank with gaps in it, plus some sand and wood. In these lakes structure is the habitat itself.
A grazing film that’s already established before the shrimp arrive. In the lake that film is the food supply, and it took a very long time to get there.
Oxygen, on purpose. Warm water starts at a disadvantage and a stocked tank only adds to it.
The exact lake readings. They’re measurements of one place on one set of days, and for one of the three lakes the published pH figures flatly disagree.
The scale. Depth, fetch and wave action are what keep silt off the rock out there. In a tank that job is yours, and it’s called Sulawesi shrimp tank maintenance.

The range we keep to for Sulawesi shrimp is 79-86°F (26-30°C), pH 7.5-8.5, 4-8 dGH, 3-6 dKH, TDS 150-250 ppm and nitrate under 10 ppm. Put that over an inert substrate, in a mature tank that already grows biofilm. These are advanced to expert animals, and nothing in the habitat above makes that easier. For the build itself, step by step, go to the Sulawesi biotope aquarium and come back here when you want to know why each step is there.

At Shrimp Aquatics, most of our Sulawesi systems currently run at TDS 150 ppm, GH 6-7 dGH and pH 7.5. We mention it because the lake figures above sit lower than that. Don’t chase a lake number down to a level your own tank can’t hold steady. Steady beats authentic here.

One last thing the habitat explains: warm alkaline water is the worst case for ammonia. The share of total ammonia present in the un-ionized form rises about ten-fold for each pH unit, and roughly two-fold for each ten degree Celsius rise in temperature across the range the criteria cover.¹¹ In the lake that never matters, because nothing is decaying on the rock. In a tank with leftover food sitting in it, it matters a great deal.

If the water still sounds like something you can hold steady for a year, the tank-bred Sulawesi shrimp we raise never had to live in a silted lake. If it doesn’t, that’s a useful answer too, and a cheaper one.