Why Are My Sulawesi Shrimp Eggs Not Hatching?

A Sulawesi clutch that never hatches lands in one of three patterns: eggs that were never fertilized, dropped eggs, or embryos that stopped part way. By the time you’re looking at the problem, that clutch has already been decided, and none of the three has a treatment. What’s still worth your attention is which pattern you’re seeing, whether the clutch has actually failed at all, and what the tank does to the next brood.

How to tell a failed Sulawesi clutch from one that’s still incubating

Start here, because most of the messages we see about eggs that won’t hatch are about clutches that are still developing. Most clutches hatch about three weeks after the eggs first appear, so give a clutch that long before you judge it. No egg hatching time for the Sulawesi lake shrimp has been published. The 2009 taxonomic revision that describes these species records what wild ovigerous females were carrying and how large the eggs were.¹ It reports no brooding duration, hatching time or hatch rate for any of them.¹ The day counts that circulate in care sheets aren’t attached to a measurement of these animals. So a clutch sitting on day 30 isn’t overdue by any standard you can defend.

So what should you watch? The clutch, not the calendar. Eggs that are still firmly attached under her abdomen and still even in color across the brood aren’t the ones telling you something went wrong. The appearances in the next section are. Until one of those shows up, the most useful thing you can do is stop lifting rocks to look at her.

How many eggs a Sulawesi shrimp carries is worth knowing before you panic about a few missing eggs. In wild Caridina dennerli, ovigerous females carried 8-14 eggs each, measured at 1.0-1.2 x 0.5-0.7 mm, from a sample of seven females.¹ These are small broods by aquarium shrimp standards, so losing two or three eggs is a different event from losing a clutch. A female who arrives at hatching with six shrimplets hasn’t failed.

What the color and timing of a lost Sulawesi clutch narrow down

Two pieces of decapod biology make the table below readable. The eggs are held in a brood chamber under the abdomen, stuck to the ovigerous setae, and kept aerated by vigorous movements of the swimmerets in freshwater prawns.² Those setae sit on the female’s own shell, and all freshwater prawns, like other crustaceans, have to regularly cast that shell in order to grow.² Separately, successful mating can only take place between ripe females that have just completed the pre-mating moult, and are therefore soft shelled, and hard shelled males.² Both points come from an FAO culture manual for freshwater prawns, not from work on Sulawesi species. Read them as biology that frames the table, not as measurements of your animals. Between them they explain three things. Why a molt takes the clutch with it. Why loose eggs lose the one thing keeping them oxygenated. And why fertilization can fail in a group that looks well stocked.

Fuzzy white growth is the reading keepers most often get backwards. In fish and fish eggs, saprolegniasis is described by extension pathologists as a secondary infection, one that follows another problem.³ Carry that framing across to a shrimp clutch, cautiously and without treating it as a diagnosis. Growth between the eggs tells you that something in the brood had already died or been damaged. It doesn’t tell you what killed it, and it isn’t a reason to dose the tank. Look for the earlier cause instead.

What to test in a Sulawesi tank while a female is still carrying

Test in the order that matters, and take the readings without netting or moving her. Ammonia and nitrite come first, because a tank that isn’t fully cycled or has lost filter capacity will show there. Then temperature, then TDS, GH and KH together, then pH. Write the numbers down, because the point isn’t one reading but whether the tank moved.

These are typical ranges for the group rather than survival limits. A number sitting inside them isn’t by itself proof that the tank was steady while the clutch was developing. Where a reading sits inside the band matters less than whether it stayed there.

• Ammonia and nitrite, on a test kit you trust, before anything else
• Temperature at the same time of day for several days, not once
• TDS, GH and KH, and the same three in the water you last added
• Surface movement and aeration. Cold water can hold more dissolved oxygen than warm water,⁴ so a tank held near the top of the Sulawesi band is working with less headroom than a cooler shrimp tank
• Don’t correct a reading that’s out of range quickly. Moving the tank back fast is the same shock as moving it out

Why the same ammonia reading is more dangerous in a warm alkaline Sulawesi tank

Total ammonia in fresh water sits in an equilibrium between the ammonium ion and un-ionized ammonia, and the un-ionized form is the one that drives toxicity. The ratio of un-ionized ammonia to ammonium ion in fresh water increases by 10-fold for each rise of a single pH unit, and by approximately two-fold for each 10 degrees Celsius rise in temperature.⁵ High external un-ionized ammonia concentrations reduce or reverse diffusive gradients and cause the buildup of ammonia in internal tissues and blood.⁵ Those criteria were derived for the freshwater assemblage the agency assessed, not for Caridina, and they set no aquarium threshold for any shrimp.

The consequence for your tank is a matter of chemistry. At pH 8.0 and 84°F, the same total ammonia reading represents a very different exposure than it does in a cooler, more acidic Neocaridina tank. That’s the practical reason a Sulawesi system has so little room for uneaten food. It’s also why the answer to a clutch problem is almost never to feed the female more.

While a female is carrying, hold that cadence and don’t increase it. If you want to change something about feeding during a brood, the change worth making is removing what’s left after an hour, not adding a second portion.

The water change and top off habits that strip a Sulawesi clutch

Molting isn’t optional, and for the reason set out above, a molt while a female is carrying ends the clutch: the eggs are attached to what she sheds. Whether stress advances a molt in these particular species isn’t something published evidence settles, so we won’t tell you that it does. What’s worth doing either way is removing the sudden changes, because those are the part of the tank you actually control.

Two routine habits move a Sulawesi tank more than most keepers expect. The first is topping off evaporation with remineralized water instead of pure RO, which lets mineral content climb over weeks. Evaporation concentrates dissolved solids in the water that remains.⁶ The second is a water change poured in at a different temperature and a different mineral content from the tank. It arrives as a local change around the animal that’s least able to move away from it.

What you can and can’t do about a Sulawesi clutch that’s already on the substrate

Honest answer first: for these species there’s no method with evidence behind it that will carry loose eggs to hatching. What those eggs lose is the mother. Many caridean shrimps and other decapods actively ventilate their egg mass by moving the pleopods frequently and quickly, with the frequency of this ventilation behavior increasing as the embryos mature.⁷ Loose eggs sitting in still water on a substrate have none of that.

Tumblers and similar improvisations circulate in the hobby. We aren’t going to publish a procedure for them here or set an expectation for how they turn out, because nothing supports either for Sulawesi lake shrimp. The more useful response is restraint. Leave the tank alone. Don’t net the female, don’t strip eggs from her, and don’t pull rockwork apart searching for the clutch. The disturbance costs you more than the eggs were worth. Siphon out eggs that have clearly broken down on your next normal maintenance pass so they aren’t one more source of waste.

If the losses go past eggs and adults start dying too, stop treating it as a breeding question. That’s a system problem, and where the severity or the uncertainty warrants it, a qualified aquatic veterinarian or a local specialist is the right next call.

When the water checks out, look at the Sulawesi group before you look at the eggs

Repeated clutches that go chalk white in the first days point somewhere your test kit can’t reach. The window for Sulawesi shrimp mating described earlier is a narrow one: the female is receptive around her pre-mating molt, and a hard shelled male has to be there for it. In a small group, or one that has been running a long time with the same few animals, there may simply be no mature male in condition at that moment. She will still extrude and carry a clutch that was never fertilized.

So count the group honestly, and be sure you can actually identify mature males. Don’t assume a balanced ratio. If the group is small enough that a female can molt with no male nearby, add a few more tank-bred Sulawesi shrimp of the same line. That’s a more direct answer than another round of water adjustments. Getting the male to female count right in the first place is most of how to breed Sulawesi shrimp.

Line vitality gets raised in breeder discussion as a cause of persistent empty clutches, particularly for colonies closed for many generations. We haven’t found evidence we’re willing to publish that connects it to hatch failure in these species. So we’ll leave it as an open question. Judge whatever you change over broods rather than over days. The clutch in front of you is settled. The tank you hand to the next one is the part that’s still open.

References

7 Sources

1. Radiation of endemic species flocks in ancient lakes: systematic revision of the freshwater shrimp Caridina from the ancient lakes of Sulawesi, Indonesia, with the description of eight new species, Raffles Bulletin of Zoology 57(2): 343-452, Lee Kong Chian Natural History Museum, 2009.
2. Farming freshwater prawns, biology chapter, FAO Fisheries Technical Papers T428, Food and Agriculture Organization of the United Nations.
3. Saprolegniasis, Texas A&M AgriLife Extension Service, Aquaculture, Fisheries and Pond Management, January 24, 2020.
4. Dissolved Oxygen and Water, U.S. Geological Survey Water Science School, updated August 24, 2026.
5. Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater, U.S. Environmental Protection Agency, Office of Water, April 2013.
6. Chloride, Salinity, and Dissolved Solids, U.S. Geological Survey, Water Resources Mission Area, March 1, 2019.
7. Is It First the Egg or the Shrimp? Diversity and Variation in Microbial Communities Colonizing Broods of the Vent Shrimp Rimicaris exoculata During Embryonic Development, Frontiers in Microbiology 10: 808, 2019.