Why Are My Sulawesi Shrimp Eggs Not Hatching?

Why didn’t your Sulawesi shrimp’s eggs hatch? A Sulawesi clutch that never hatches lands in one of three patterns: eggs that were never fertilized, eggs she dropped, 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 really 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

Watch the eggs, not the calendar, because a clutch that hasn’t hatched yet is often still developing. Most clutches hatch about three weeks after the eggs first appear, so give a clutch that long before you judge it. One keeper’s female arrived already carrying, held her eggs for about three weeks, and then the eggs were simply gone and little shrimplets were there instead.

That figure comes from keepers, because no study has published a Sulawesi shrimp egg hatching time. The 2009 taxonomic revision of these species records what wild ovigerous females were carrying and how large the eggs were. It reports no brooding duration, hatching time or hatch rate for any of them.¹ Care sheet day counts aren’t tied to any 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 itself. 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.

Before you panic about a few missing eggs, it helps to know how many eggs a female Sulawesi shrimp can carry per brood. In wild Caridina dennerli,¹ 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. Those are small broods by aquarium shrimp standards, so losing two or three eggs is a different event from losing a clutch. A female who reaches hatching with six shrimplets hasn’t failed.

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

Color and timing tell you which failure you’re looking at. Three things in the table follow from how decapods carry their eggs. A molt takes the clutch with it. Loose eggs lose the one thing keeping them oxygenated. And fertilization can fail in a group that looks well stocked. The reason, from work on freshwater prawns, not Sulawesi shrimp: the eggs ride on setae on the female’s own shell, her swimmerets keep them aerated, and mating needs a just-molted female and a hard-shelled male.²

Fuzzy white growth is the reading keepers most often get backwards. In fish and fish eggs, extension pathologists call saprolegniasis a secondary infection.³ On a shrimp clutch, take that as a hint, not 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 ammonia and nitrite first. Then check temperature, then TDS, GH and KH together, then pH, and take every reading without netting or moving her. Ammonia and nitrite lead because a tank that isn’t fully cycled, or has lost filter capacity, will show there. Write the numbers down. One reading tells you little; what you want to know is whether the tank moved.

These are typical ranges for the group, not survival limits. A number sitting inside them doesn’t prove by itself 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 near the top of the Sulawesi band has less headroom than a cooler shrimp tank.
• Don’t rush to correct a reading that’s out of range. 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

Warm, alkaline water pushes more of the ammonia into its toxic, un-ionized form. 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. According to the EPA’s freshwater criteria,⁵ 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.

For your tank, that’s plain chemistry. At pH 8.0 and 84°F, the same total ammonia reading means a very different exposure than it would 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.

So treat any reading above 0 while she’s carrying as a husbandry problem to find, not something to dose. In a settled tank it usually traces back to uneaten food, a filter that was disturbed or cleaned, or a bioload the system hasn’t caught up with.

While a female is carrying, hold that cadence and don’t increase it. If you want to change something about feeding during a brood, take out what’s left after an hour. Don’t add a second portion.

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

A molt while she’s carrying ends the clutch. So cut the sudden changes you control, chiefly an unmatched water change, and a top off with mineralized water instead of pure RO. Matching every bucket to the tank on temperature, TDS, GH and KH is the main fix when a Sulawesi shrimp is dropping eggs. It protects a clutch that’s still developing in exactly the same way.

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

No method with evidence behind it will carry loose Sulawesi eggs to hatching. What those eggs have lost is their mother. Many caridean shrimps ventilate their eggs with their pleopods, more often as the embryos mature.⁶ 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 the rockwork apart searching for the clutch. The disturbance costs you more than the eggs were worth. On your next normal maintenance pass, siphon out eggs that have clearly broken down so they aren’t one more source of waste.

If the losses go past eggs and adults start dying too, it’s no longer 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 at the group, somewhere your test kit can’t reach. The mating window 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’s run for years with the same few animals, there may be no mature male in condition at that moment. She’ll still extrude and carry a clutch that was never fertilized.

So count the group honestly, and make sure you can actually identify mature males. 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. Don’t swing to a crowd of males, though; the ratio worth aiming for is part of what to check when a Sulawesi female is dropping eggs. Having a mature male in the group when each female molts is the first step in how to breed Sulawesi shrimp.

Line vitality comes up in breeder discussion as a cause of persistent empty clutches, particularly in 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. Whatever you change, judge it over broods, not days. The clutch in front of you is settled. The tank you hand to the next one is the part that’s still open.

What the research says about Sulawesi eggs not hatching

Several of the sources behind this page are on other animals. Read them as mechanism, not as measurements of your shrimp. An FAO culture manual for freshwater prawns² describes the eggs held in a brood chamber under the abdomen. They’re stuck to the ovigerous setae and kept aerated by vigorous movements of the swimmerets. 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. According to the same manual,² 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.

A paper on broods of the vent shrimp Rimicaris exoculata⁶ notes that many caridean shrimps and other decapods actively ventilate their egg mass by moving the pleopods frequently and quickly. That ventilation gets more frequent as the embryos mature. The fuzzy growth reading borrows from fish. Extension pathologists describe saprolegniasis in fish and fish eggs as a secondary infection, one that follows another problem,³ so carry that framing across to a shrimp clutch only with caution.

The ammonia figures come from the EPA’s freshwater criteria. Those criteria also state⁵ that high external un-ionized ammonia concentrations reduce or reverse diffusive gradients and cause the buildup of ammonia in internal tissues and blood. They were derived for the freshwater assemblage the agency assessed, not for Caridina, and they set no aquarium threshold for any shrimp.

References

6 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. 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.