Best Substrate for Sulawesi Shrimp: Inert, Dark and Laid Thin

Got the mineral mixed and the water dialed in, and now you’re stuck on what goes on the bottom? Use an inert bed: crushed lava rock or basalt gravel for most Sulawesi tanks, dark, coarse enough to stay open and thin enough to siphon, or inert sand where you want a smooth floor. In this tank the water sets the parameters and the substrate stays out of it. The two beds behind most losses are the ones sold as helpful, an active bee shrimp soil and a crushed coral or aragonite layer, because both move numbers you’ve already set.

Sulawesi shrimp are lake Caridina from the Malili and Poso systems, kept in warm, mildly alkaline, moderately mineralized water. Those values come out of a bottle, not out of the gravel. A Sulawesi shrimp mineral supplement dissolves into RO water within seconds and buffers the pH at around 7.5. It raises carbonate and total hardness together at a fixed ratio of KH to dH of 0.42 to 1.0.¹ So the mix you make is the mix you get. Carbonate hardness is the water’s buffering capacity, its ability to neutralize acid and hold a fairly stable pH. It depends on dissolved bicarbonates, carbonates and hydroxides being present in the water column.² Once you’ve paid for that control, a substrate that adds or removes those same ions is working against you.

So how should you read that substrate row? As a filter, not a recommendation. Anything you put on the bottom either leaves the table alone or it doesn’t, and everything below applies that one test.

Bee shrimp soil will pull a Sulawesi tank into the wrong water

An active bee shrimp soil lowers pH and strips carbonate hardness, which is the opposite of what a Sulawesi tank needs. It’s the mistake that ends colonies in the first month, and it usually arrives with good intentions, because the bag on the shop shelf says shrimp substrate. Active shrimp soils are engineered products with a stated chemical job. Dennerle recommends its Shrimp King Active Soil for bee shrimp such as Crystal Red, Red Bee and Tiger Bee. Its own product information says the soil lowers the pH value and stabilizes it in the slightly acidic range of about 6.0-6.5 for those bee shrimp. It reduces carbonate hardness for the same bee shrimp to roughly 0-2 dKH, depending on the source water.³ The same page calls it a natural ion exchanger suited to species that love soft, slightly acidic water. That’s the water Bee and Crystal Caridina need, pH 5.8-6.8 with KH 0-2 dKH, and every part of it points away from the Sulawesi table above.

The soil doesn’t fail in your tank. It succeeds, at the job it was built for. You mix water to pH 7.5-8.5 with KH 3-6 dKH, then pour it over a bed whose whole function is to consume carbonate and release acidity. The buffer you paid for gets spent holding the substrate off. What the shrimp feel isn’t a stable number at all but a slow drift, and drift is the thing this group handles worst.

Can crushed coral or aragonite hold a Sulawesi tank alkaline?

Not in a way you can control, because a carbonate bed keeps adding hardness with no dial on it. Plenty of care sheets, including pages ranking today for this exact question, recommend crushed coral or aragonite sand anyway. It pushes pH up, and Sulawesi shrimp want it up. The logic is sound. The execution isn’t.

Water hardness is the amount of dissolved calcium and magnesium in the water. Water picks those minerals up by dissolving them out of the rock and soil it moves through.⁴ A calcium carbonate bed in your tank is that same process, running nonstop, in a closed volume of 10 or 20 gallons. It doesn’t stop when GH reaches 8 dGH. You can’t mix to a target and hold it, because the floor then modifies whatever you mix, and the only way to find out by how much is to keep testing and keep chasing. In a group that wants TDS 150-250 ppm and GH 4-8 dGH held steady, a floor that always pushes one way is a permanent argument with your own water change.

But don’t the shrimp need calcium to molt? They do, and the calcium reaches them through the water either way. For crustaceans the major source of calcium used for exoskeleton calcification is exogenous, meaning the water the animal lives in, with stored premolt reserves and diet contributing less.⁵ Your mineral salt already delivers calcium as part of GH. A second, uncontrolled source doesn’t make the first one work any better.

Lava gravel, inert sand and bare bottom compared for a Sulawesi tank

With chemistry off the table, the choice comes down to grazing surface, traction and how easy the floor is to keep clean. All three options below are chemically fine, so pick by how you actually run the tank.

Why crushed lava rock is the low-risk default

Crushed lava rock and basalt gravel are inert, so the mix you made is the mix that stays. They’re also rough and full of open pores, which gives biofilm and algae somewhere to settle, and that grazing layer is most of what these shrimp eat between feedings. Dark grain has one more practical advantage: waste and shed shells stay visible against it, and a molt you can see is a molt you can count.

Rinse any volcanic gravel in RO water until the water runs clear before it goes in. Crushed rock carries fine dust from processing, and that dust is the one thing about this substrate worth handling with care.

When inert sand is the better floor

Sand sold as inert, such as washed quartz pool filter sand, leaves your water alone in the same way. It suits a keeper who wants a flat, easily read floor and siphons it regularly. Check what you’re buying first, because a carbonate sand sitting on the shelf beside it belongs in the section above. The trade is that fine, smooth grain packs down, so a sand floor rewards frequent light siphoning. It also shows every bit of waste, which is a feature if you’re watching the tank and a nuisance if you aren’t.

Skip pale, bright sands. They make waste harder to spot against a light background, and they wash out the contrast these lines are kept for.

What a bare bottom really costs the shrimp

Breeders run bare glass for a reason: nothing builds up where you can’t see it, and a siphon reaches every square inch of the floor. If you’re running a grow out tank you check twice a day, that hygiene is worth more than any substrate benefit.

For a display colony it’s a harder sell. Bare glass offers no grazing surface at all, so the whole food supply moves onto hardscape, filter media and whatever you add. A shrimp that grazes for a living now depends on you not overfeeding Sulawesi shrimp in a warm tank. Rock, ceramic media and a mature sponge can carry that load, but you have to supply the surface on purpose instead of getting it from the floor.

Set the bed up before the animals arrive. Every line of tank-bred Sulawesi shrimp we stock is rated advanced or expert, and rebuilding a floor is far harder once a colony is grazing on it.

Keep a Sulawesi bed thin enough to siphon the whole floor

Depth causes more Sulawesi substrate failures than material does. A deep bed traps fine waste below the layer you can reach, and in this group that matters more than it would in a cool, soft water tank. The reason is what warm alkaline water does to the ammonia that waste produces. Total ammonia in water splits between the ammonium ion and un-ionized ammonia, and it’s the un-ionized form that drives toxicity. The ratio of un-ionized ammonia to ammonium ion in fresh water increases roughly 10-fold for each rise of a single pH unit. It rises about two-fold for each 10 degrees Celsius rise in temperature from 0 to 30 degrees Celsius.⁶ That relationship comes from the freshwater assemblage the EPA studied, not from shrimp, and it sets no threshold for any Caridina. The direction is what counts. The same total ammonia reading means something harsher in a Sulawesi tank at pH 8.2 and 84°F than in a Bee shrimp tank at pH 6.5 and 70°F.

So the working rule is a question you can answer by looking. Can you see the glass through the bed in places? Lay it so you can. A siphon should reach the bottom everywhere, and nothing on the floor should be hidden from you. If you have to dig deep into the bed to clean it, it’s too deep for this tank.

• Every part of the floor is reachable with a siphon without digging.
• Grain is coarse enough that it doesn’t pack into a solid layer.
• Waste and shed shells stay visible on top.
• A planted style deep bed built for root feeders.
• Fine silt or very fine sand that compacts and slows flow through the bed.
• Large cobbles with gaps that swallow waste you can’t reach.

Changing the substrate under a stocked Sulawesi colony without a crash

Put stability first: if soil or crushed coral already sits under a living colony, the bed isn’t your most urgent problem. Pulling a bed out of a stocked tank stirs up everything it has trapped, disturbs the bacteria living on it and changes several things at once. That’s the pattern these shrimp handle worst.

1. Test first and write the numbers down. Confirm ammonia and nitrite are at zero and record pH, GH, KH, TDS and temperature, so you know which way the current bed is pushing.
2. Set up the new bed in a separate cycled tank instead of rebuilding the occupied one, and give it time to grow visible grazing surface before anything moves.
3. Match the new tank’s water to the readings you took, not to a chart, so the shrimp meet the same chemistry they’re living in now.
4. Move the animals, along with a mature sponge or established rock, once the new system holds those readings steady on its own.
5. Correct the water chemistry afterwards, slowly, in the new tank. Fixing chemistry and moving house on the same day is two shocks, not one.

If a separate tank isn’t possible, the fallback is to remove the old carbonate or soil bed in stages over several weeks, testing between each stage. It’s slower, and it’s still the safer version of the same job.

References

6 Sources

1. Sulawesi Mineral 7,5, Minerals and trace elements, SaltyShrimp (Garnelenhaus), product information page, no revision date shown.
2. Alkalinity and Water, U.S. Geological Survey Water Science School, updated August 24, 2026.
3. Shrimp King Active Soil, Dennerle, product information page.
4. Hardness of Water, U.S. Geological Survey Water Science School, updated August 24, 2026.
5. Biomineralizations: insights and prospects from crustaceans, ZooKeys 176, 2012.
6. Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater (2013), U.S. Environmental Protection Agency, Office of Water, April 2013.