Why did your Sulawesi shrimp drop her eggs? There’s rarely one cause to guess at, and what she left behind tells you which of three events you’re dealing with: eggs held in a cast shell, loose eggs under a bare female, or a clutch that thins while she’s still carrying. Each one has a different answer, and one of them may not be a problem at all.
Check whether your Sulawesi shrimp molted the clutch off or dropped it
Look for her shed shell first, before you reach for the test kit. A shrimp grows only by casting its whole shell, and between molts the clutch rides under the female’s abdomen, stuck to fine egg-bearing hairs and aerated by her swimmerets.1 The brood starts on a molt too: in caridean shrimp the female mates just after a prespawning molt and spawns soon afterward.2
So the clutch is glued to a shell she’s going to shed eventually. The whole question is whether that shell comes off before the eggs hatch or after. That’s why the exuvia is the first thing to look for on the morning you notice she’s bare. Give yourself a full day of looking before you decide no molt happened, because a cast shell in a rockwork tank is easy to miss.
Count the days, too. Keepers put a Sulawesi brood at about three weeks from berried to hatch. One keeper’s female arrived berried, carried her eggs for about three weeks, and then one day the eggs were gone and little shrimplets were there instead.
| What you find | What it points to | What to look at next |
|---|---|---|
| An intact cast shell with eggs still held in it | A molt ended this brood, so the molt is what needs explaining, not the eggs | Everything you did to the tank in the two or three days before: water change, top off, heater change, a filter that was cleaned or restarted |
| Loose eggs on the substrate and a bare female, no exuvia found | Either the eggs came off the setae without a molt, or the shed shell hasn’t been found yet | Keep looking for the exuvia for another day, and meanwhile check what could have knocked her about: flow at rock level, a startled dash, a heavy tankmate |
| She’s still carrying, but the clutch is visibly smaller than it was last week | Loss from an intact brood, which is a different problem from a clutch that came off all at once | Whether anything is stopping her grooming the eggs, and whether the loss is more than the small amount that normally goes missing during incubation |
| Several mature females lose clutches inside the same few days | The only thing more than one animal shares is the tank itself | Your maintenance record, not any individual shrimp |
How many eggs a Sulawesi female carries in the first place
Fewer than you might expect. Check how many eggs female Sulawesi shrimp carry per brood before you call a few missing eggs a dropped clutch. The wild females measured in the 2009 species revision carried small broods, as few as 8 eggs in some species.3 If you’re counting against a Neocaridina or Bee guide, a thin brood will look like a loss when it isn’t one.
Match replacement water to the tank before it costs a berried female her clutch
Most of what you can actually control sits here, and it’s about the size of the step more than the destination. A berried female has to keep her shell until the eggs hatch. The events that most often come before a lost clutch are the ones that arrive all at once. A big water change with unmatched water. A top off that moved the mineral load. A heater turned up. A filter restarted after a clean. The values below are the group ranges these species are kept in. Treat them as the band you’re holding, because chasing them is what produces the swings.
| Temperature | 79-86°F (26-30°C) |
|---|---|
| pH | 7.5-8.5 |
| GH | 4-8 dGH |
| KH | 3-6 dKH |
| TDS | 150-250 ppm |
Test the replacement water and the tank water side by side before the two meet. Keep the change small enough that a mistake in the mix can’t move the tank far. If the two don’t agree, fix the bucket before any of it goes in.
Where a molting female gets the minerals for her new shell
Mostly from the water around her. In crustaceans the calcium for a new shell comes mainly from outside the animal, with stored reserves and diet adding less.4 That’s the practical reason to hold GH inside 4-8 dGH and not let it drift down between water changes. A female pushed into a molt needs what’s dissolved around her at that moment, and a tank that’s been slowly softening is a bad place for that to happen.
Dissolve Sulawesi minerals completely before that water reaches the tank
When you remineralize RO water for Sulawesi shrimp, the salts are slow to go into solution. Half-dissolved salt keeps dissolving once it’s in the aquarium, which turns one water change into several days of drift. SaltyShrimp’s own instructions for Sulawesi Mineral 8.5 are explicit about it: the salt almost totally dissolves when CO2 is added over roughly 3-4 days at about one bubble per second.5 The water then needs at least three hours on an air stone to drive the CO2 back out before use. The product raises carbonate and total hardness together at a ratio of KH to dGH of 0.78 to 1.0.5 Whichever product you use, mix it outside the tank, let it finish, and test the finished water.
Top off evaporation with pure RO water
Evaporation takes the water and leaves the dissolved solids behind, concentrating them in what’s left.6 So topping up with mineralized water causes a slow drift toward high TDS in a Sulawesi tank, with rising hardness, while the water line looks exactly the same. Nobody notices until a reading comes back higher than the number they set months ago. Top off with pure RO or deionized water, save the mineralized water for real water changes, and check TDS against what you set.
Why turning the heat up in a Sulawesi tank works against a berried female
Because heat can shorten the gap between molts, and a berried female needs her brood to finish before the next shell comes off. These shrimp are kept warm, and if you want the eggs to hatch sooner, the top of the range is tempting. Work on other crustaceans points the wrong way: crabs reared warmer molted more often and grew less per molt.7 A shorter interval between molts is exactly what a female carrying eggs doesn’t need.
Heat costs you oxygen as well. Cold water holds more dissolved oxygen than warm water.8 A tank at 79-86°F (26-30°C) is already at the thin end of that curve while the brooding female fans her clutch around the clock. Good surface movement and gas exchange are worth having in a warm Sulawesi tank for that reason alone. Nothing here shows oxygen cost you a particular clutch. What none of it supports is raising the temperature to speed anything up.
What warm alkaline Sulawesi water does to a trace ammonia reading
Warm alkaline water puts more of any ammonia into its toxic form.9 So even a trace in a Sulawesi tank is a husbandry problem to fix, usually uneaten food or a disturbed filter, not something to dose. Why the same reading does more harm here, and what to test while she’s still carrying, is part of the answer for Sulawesi eggs that aren’t hatching.
Don’t treat a dropped clutch
Egg loss isn’t a diagnosis, and there’s no medication for it. Copper and several fish medications are dangerous to shrimp, and dosing a tank on the strength of a lost brood adds a second problem to the first. If shrimp are also dying, molting badly or behaving abnormally, that’s a separate question. Take it to a qualified aquatic vet or an experienced local keeper, with your actual test results.
When a female keeps her clutch but loses eggs from it
A clutch that thins out over days usually means something is getting in the way of her cleaning it. A brooding female doesn’t only carry her eggs, she grooms them, and in shrimp studies females kept from cleaning their embryos lost many of them to fouling.10
That changes what you look for. Visible fuzz or growth on the eggs is what fouling looks like. Silt settling on the brood. A female who spends the day wedged in a crevice because something keeps startling her. A tank so freshly disturbed that fine material is still raining down. All of it points the same way, and the fix is the boring one: settle the tank, leave her alone, keep organic waste from building up in the rockwork, and let her do the work she’s built for.
Before you change anything, ask how much is actually gone. Some loss during incubation is normal, and it’s been measured in a sand shrimp, though not in Sulawesi species.11 A handful of eggs missing across the weeks she carries may be no more than that. A clutch that’s visibly smaller from one week to the next is the one worth the checks above.
Whether your Sulawesi group has too many males for the number of females
A male-heavy group can put a newly molted female under pressure she doesn’t need. In most shrimps, mating happens right after the female’s premating molt, and that short window is understood to limit harassment that can injure or even kill her.12 A soft, freshly molted female chased by several males is the moment worth designing around, and a group weighted toward males is what creates it.
At Shrimp Aquatics, when we can sex the shrimp with reasonable confidence, we usually build a Sulawesi breeding group with either 2 males to 8 females or 3 males to 7 females. We use a female-heavy group to reduce mating pressure on newly molted females, which are still soft and vulnerable, and we confirm sex from more than one visible cue before setting the ratio. That same female heavy ratio is the starting point in how to breed Sulawesi shrimp.
That’s how we put a group together, not a diagnosis of what happened in your tank, and a male-heavy colony can certainly still breed. If you decide to even yours out, we’d add females instead of trying to remove male Sulawesi shrimp. Give any new tank-bred Sulawesi shrimp water that matches what they’re moving into before they go across.
The narrow window cuts the other way too. A female who molts with no mature male nearby misses it. A group short of males has a fertilization problem, and its signs belong with Sulawesi shrimp eggs not hatching, not with a dropped clutch.
What’s worth changing after a lost Sulawesi clutch
Only the thing you can name. If the evidence points at a molt and you know what change came before it, correct that change and leave the rest of the tank alone. Smaller water changes, matched temperature and TDS, RO for top offs, minerals finished before they’re used. If you can’t name anything, the honest answer is that a single lost clutch from a settled colony often has no recoverable cause. Leave the parameters where they are and watch the next brood.
What doesn’t help is the thing most people do next. Chasing numbers after a lost clutch produces exactly the swings that make the next one less likely. A female who has just lost a brood will molt and can carry again. So write down the date, what she looked like, whether an exuvia turned up and what you’d done to the tank that week. Two or three of those notes tell you far more than any single incident. If a pattern shows up, it’ll be in that log, not in a care sheet.
What the research says about Sulawesi shrimp dropping eggs
Almost none of the brood research behind this guide was done on Sulawesi Caridina. Read it as the mechanism, not as a measurement of your tank. In freshwater prawns, the clutch is attached to the ovigerous setae under the female’s abdomen and kept aerated by the constant beating of her swimmerets.1 In caridean shrimp generally, the female mates just after a parturial, or prespawning, molt, spawns soon afterward and then carries the fertilized embryos for an extended incubation.2 Mating behavior in most shrimps happens at that premating molt, when males encounter just-molted receptive females.12
On shell building, a review of crustacean biomineralization names the surrounding water as the major source of calcium for a new exoskeleton. Stored reserves and diet contribute less.4 On temperature, lesser blue crabs reared at elevated temperature showed both a shorter intermolt period and less growth per molt.7 The authors note that would mean a smaller size at maturity if the pattern held through to the pubertal molt.7
On egg care, females use their general grooming limbs on their incubated embryos.10 That grooming keeps the brood free of smothering sediment and of fouling by bacteria, fungi, sessile protozoans and microscopic algae.10 For normal loss, the sand shrimp Crangon uritai lost an estimated 5.56 percent of its eggs and 8.44 percent of brood dry weight over embryonic development, independent of female size.11 Nobody has published the same figure for Sulawesi species.
References
12 Sources
- Farming freshwater prawns, Chapter 1 Biology, Food and Agriculture Organization of the United Nations, FAO Fisheries Technical Paper 428.
- Chemical Communication in Decapod Shrimps: The Influence of Mating and Social Systems on the Relative Importance of Olfactory and Contact Pheromones, R. T. Bauer, in Chemical Communication in Crustaceans, Springer, 2011, hosted PDF copy.
- Radiation of endemic species flocks in ancient lakes: systematic revision of the freshwater shrimp Caridina from the ancient lakes of Sulawesi, Indonesia, Raffles Bulletin of Zoology 57(2), Lee Kong Chian Natural History Museum, 2009.
- Biomineralizations: insights and prospects from crustaceans, ZooKeys 176, 2012.
- Sulawesi Mineral 8,5, minerals and trace elements, SaltyShrimp, manufacturer product information page.
- Chloride, Salinity, and Dissolved Solids, U.S. Geological Survey, March 1, 2019.
- Elevated temperature induces a decrease in intermolt period and growth per molt in the lesser blue crab Callinectes similis, Journal of Crustacean Biology 39(1), 2019, abstract.
- Dissolved Oxygen and Water, U.S. Geological Survey Water Science School, June 5, 2018.
- Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater, U.S. Environmental Protection Agency, Office of Water, April 2013.
- Ray Bauer research: grooming morphology and behavior, R. T. Bauer, University of Louisiana at Lafayette, research page.
- Fecundity and Brood Loss of Sand Shrimp, Crangon uritai, Journal of Crustacean Biology 31(1), 2011, abstract.
- Ray Bauer research: mating behavior and sexual strategies, R. T. Bauer, University of Louisiana at Lafayette, research page.
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