Is there a fish that’s safe to keep with your Sulawesi shrimp? No fish belongs in a Sulawesi shrimp tank: some eat your adults, the peaceful ones eat the shrimplets, and the rest quietly take the biofilm and grazing time the colony needs. If you want fish, give them their own tank and keep the Sulawesi shrimp on their own. It’s not the answer anyone hopes for, so here’s why each kind of fish fails.
Why fish waste hits harder in warm, alkaline Sulawesi water
Fish waste does more harm in a Sulawesi tank because warm, alkaline water pushes more of the ammonia it produces into the form that’s toxic.
| Temperature | 79-86°F (26-30°C) |
|---|---|
| pH | 7.5-8.5 |
| GH | 4-8 dGH |
| KH | 3-6 dKH |
| TDS | 150-250 ppm |
| Nitrate | Kept under 10 ppm as a working target |
| Difficulty | Advanced to expert |
Total ammonia in any tank sits in a balance between ammonium, which is relatively benign, and un-ionized ammonia, the form that drives toxicity in aquatic animals. That balance moves. In fresh water the ratio of un-ionized ammonia to ammonium rises roughly ten-fold for each single pH unit, and about two-fold for each 10 degrees Celsius of warming across the 0-30 degrees Celsius range.1 Now run that on your own tank. At pH 8 and 84°F, the same test-kit reading means far more of the dangerous form than it would in the soft, acidic tank most community fish advice was written for.
So the problem is your margin, and it’s thin. A bioload a planted tetra tank absorbs without anyone noticing is one you can’t afford here. A kit that says 0.25 ppm total ammonia is telling you something different in this tank than it would in that one.
Warmth costs you on the other side too. Cold water holds more dissolved oxygen than warm water,2 so a Sulawesi tank is already running near the bottom of the oxygen range the hobby usually deals with. A school of active fish adds oxygen demand to a system that has less to give.
Before you add anything
If ammonia or nitrite ever reads above zero in a stocked Sulawesi tank, stocking isn’t the question to ask. Fix the cycle first, and slowly, because a fast correction is its own shock.
The fish that will eat adult Sulawesi shrimp
Bettas, gouramis, larger cichlids and anything with a mouth wider than a shrimp carry a real predation risk to adult Sulawesi shrimp. Nothing in that group is marketable as shrimp safe, and we don’t treat any of it as a maybe.
| Group | What actually happens |
|---|---|
| Bettas and gouramis | Slow, deliberate hunters that work rockwork and crevices, which is exactly where these shrimp sit. A shrimp that has just molted has no defense at all. |
| Cichlids, large or small | Material predation risk on adults. The dwarf species that people propose as a compromise also want water nothing like this. |
| Puffers, pea puffers included | We wouldn’t put one in a tank with shrimp or rabbit snails, at any size. Their whole feeding style is aimed at small hard-shelled animals. |
| Anything over a few inches | If the shrimp fits in the mouth, assume it will eventually go in the mouth. Gape is the rule, not temperament. |
You’ll read that someone’s betta ignored the shrimp for six months. We believe those accounts. The trouble is that you only learn you had the exception after the fact, and the price of being wrong is a colony you spent a year building. That’s a lot to stake on one betta’s good manners.
Peaceful nano fish don’t eat adults, they end the next generation
Small rasboras, ember tetras, chili rasboras, guppies and endlers won’t hurt an adult Sulawesi shrimp, but they’ll eat the shrimplets that should become your next generation. They’re visual micro-predators, and a newly released shrimplet is exactly the size of the food they hunt.
Keepers often get away with that in a cherry shrimp tank. You won’t here, because Sulawesi clutches are small. In wild Caridina dennerli, ovigerous females were recorded carrying 8-14 eggs per brood, with eggs measuring 1.0-1.2 x 0.5-0.7 mm. Across the lake species in the same revision, per-species clutches ran from single figures to a few dozen, and higher in a handful of deep-water species.3 Those are small wild samples, not a species constant, but the scale is the point. A clutch that size can’t absorb a fish eating the young.
What you’ll actually see is a tank that looks fine. The adults are there, they graze, they molt, and a year later there are fewer of them and no juveniles anywhere. The adults lived as long as Sulawesi shrimp live while the fish ate every recruit. That’s why we say the peaceful species do the most damage: nothing about the tank looks wrong while it’s happening.
The phrase to distrust
Generally shrimp safe means lower risk to adults. It has never meant safe for shrimplets, and no fish sold under that label is safe for a Sulawesi colony that has to breed to survive.
Fish that never touch your shrimp still take their food and their nerve
Even a fish that won’t eat your shrimp still takes their food and unsettles them. Otocinclus is the usual candidate, sometimes pygmy corydoras or a kuhli loach. Predation risk is low, and that’s a fair reading, but it isn’t the whole bill.
Sulawesi shrimp graze aufwuchs, algae and biofilm off rock and glass, and in a mature tank that growth is most of their food. An otocinclus eats the same film, all day, and it’s much better at it. Corydoras add competition and can still take shrimplets. Everything in this group works the substrate, which is where your shrimp live.
Then there’s the part keepers underrate. These shrimp are shy. With fish moving through the tank, they spend the day in the dark gaps between rocks, away from the lit surfaces where the biofilm actually is. Nothing eats them. They just stop feeding properly, and grazing time is the whole point of the setup you built.
Are the lakes’ own fish a safe exception?
No. Sailfin silversides, ricefish and the Matano gobies share the shrimp’s water chemistry, so the biotope logic sounds airtight. We still wouldn’t put them in a Sulawesi shrimp tank.
The literature describes what these fish eat in a lake, which tells you nothing about whether they can share a tank. One published stomach-content study of Telmatherina prognatha in Lake Matano recorded insects, debris and plankton as the main food items across a year of sampling.4 That’s a lake with enormous volume, deep water and endless rock for a shrimp to disappear into. Your tank has none of that. Squeeze an active, hungry fish and a slow, shy shrimp into a few feet of glass with no escape route, and the wild relationship stops being a useful guide.
We couldn’t find a published compatibility trial for any fish kept with lake Caridina in an aquarium. When the hobby doesn’t know, we’d rather say so than borrow a lake study and call it a tankmate recommendation.
What happens the day you have to medicate the fish
The moment you reach for a fish treatment, the shrimp become the problem, and fish kept with Sulawesi shrimp get sick sooner or later. That’s no knock on anyone’s husbandry. It’s what happens over a few years of keeping fish.
Copper is the clearest case. Elevated copper is toxic in aquatic environments and may adversely affect fish, invertebrates, plants and amphibians; acute effects include mortality, and chronic exposure can reduce survival, reproduction and growth.5 Its bioavailability, and so its toxicity, shifts with pH, alkalinity, dissolved organic carbon and hardness. So the number printed on a bottle doesn’t transfer cleanly between two tanks with different water. Plenty of ordinary fish medications carry copper or other actives that invertebrates tolerate poorly. Read the actual ingredient list, because it matters more than the shrimp-safe badge on the front.
We won’t give you a dose, because dosing an invertebrate tank isn’t something to work out from an article. Realistically, treating the fish properly in a fish-and-shrimp tank usually means moving them. By then you’re running the separate tank you could have set up at the start.
What can share a Sulawesi tank, and what to do if fish are already in there
A shrimp-only Sulawesi tank gives the colony its best chance of carrying on. A Sulawesi community tank with fish can keep the adults alive for a year or two, but not the colony.
A shrimp-only Sulawesi tank
Low bioload, stable chemistry, biofilm that belongs to the shrimp, and juveniles with a real chance of reaching adulthood. It’s the setup we’d tell a friend to build for Sulawesi shrimp.
A Sulawesi community tank
More waste in water that punishes waste, a food supply split with something faster, and a colony that stops recruiting. You may keep the adults alive for a year or two. You won’t keep the colony going.
For tankmates, the short list really is short. Rabbit snails from the same lakes, Tylomelania spp., want warm alkaline water just like the shrimp, so nothing has to be compromised to keep both. They clear decaying matter and they don’t hunt. Nerites can work on chemistry, though check the species instead of assuming, and skip assassin snails, which prey on other snails. Once fish are off the table, rabbit snails and nerites are the realistic picks, which lines up with the best tank mates for Sulawesi shrimp.
If what you actually want is movement in the tank, there’s one option we’ve used ourselves.
In some of our Sulawesi systems at Shrimp Aquatics we keep about five Neocaridina, and we have observed the Sulawesi shrimp remain more visible, or retreat less, when people approach the tank. This still needs temperature overlap, enough grazing surface and stocking room for both groups, so it isn’t a free addition, and we wouldn’t put a breeding Neocaridina colony in a specialist Sulawesi tank.
Bee and Crystal Caridina are a different question with the same answer: their soft, acidic, cooler water is incompatible with this tank, and sharing the genus Caridina changes nothing about that.
Already have fish in with your shrimp? Don’t tear the tank apart today. Work through it in order:
- Move the fish to their own tank, matched on temperature and chemistry, instead of rehoming the shrimp into an immature system.
- Cut feeding back toward what the shrimp actually use, since the fish portion was inflating the waste load.
- Test ammonia and nitrite, then temperature, pH, GH, KH and TDS, and correct anything out of line slowly over days.
- Give the rockwork a few weeks with the lights on a normal cycle so the grazing surfaces recover before you judge the colony.
- Don’t add a second fish species to balance the first, and don’t treat the tank for anything you haven’t identified.
Then leave it alone and watch. Juveniles on the rock are the signal you’re looking for, and if they come, they come on the tank’s schedule, not yours.
References
5 Sources
- Aquatic Life Ambient Water Quality Criteria for Ammonia, Freshwater, U.S. Environmental Protection Agency, Office of Water, April 2013.
- Dissolved Oxygen and Water, U.S. Geological Survey, Water Science School, updated August 24, 2026.
- 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, 2009.
- Food habits of endemic opudi fish (Telmatherina prognatha, Kottelat 1991) in Matano Lake, South Sulawesi, Indonesia, Biodiversitas Journal of Biological Diversity 21(4): 1373-1378, 2020.
- Supplementary Training Materials for Aquatic Life Criteria, Copper, Background, U.S. Environmental Protection Agency, Office of Water, updated May 6, 2026.
