24–48 hrs Time from symptom to death in fast-moving infections

0.25 ppm Ammonia level that measurably suppresses shrimp immunity^[1]

2–4 hrs Window to photograph DOA livestock for a valid claim

2–4 wks Minimum quarantine period for all new additions

Why Shrimp Are Vulnerable

Bacteria are a natural and necessary part of any aquarium ecosystem. Beneficial nitrifying bacteria in your biofilter convert toxic ammonia to nitrite and then to nitrate — the foundation of a healthy tank. The danger lies with opportunistic pathogenic bacteria that are always present in small numbers and are held in check by healthy shrimp and stable water conditions.

Shrimp are invertebrates with relatively simple immune systems. Unlike vertebrates, they lack adaptive immunity — they cannot produce antibodies or mount a targeted immune response to a specific pathogen. Their defense is largely cellular and nonspecific, meaning when environmental stressors weaken it, all pathogens gain an equal advantage at once.

This is why most bacterial infections in shrimp tanks are secondary: the bacteria was likely already present, but a triggering event — a water parameter spike, a failed molt, a new introduction, or chronic overfeeding — created the conditions for it to overwhelm the colony. Treating only the bacteria without addressing the root stressor almost always leads to recurrence.^[2]

Dwarf shrimp showing signs of chitinolytic bacterial (rust) disease

A shrimp showing characteristic signs of chitinolytic bacterial disease — also called rust or shell disease. Note the discoloration and lesion-like markings on the carapace that result from chitinase enzyme activity breaking down the outer shell. Image: AquariumBreeder.com

⚠️ Not all sudden losses are bacterial. Copper contamination (from medications, piping, or some tap water sources), pesticide residue on new plants, ammonia spikes in an uncycled tank, and drastic pH swings can all produce rapid, identical-looking die-offs. Always test water first — ammonia, nitrite, nitrate, pH, and temperature — before assuming an infection.

Warning Signs & Symptoms

Early detection is everything. Bacterial infections often progress through recognizable stages — catching it at stage one or two can mean the difference between losing a few individuals and losing the entire tank. Make a habit of observing your shrimp during feeding so that behavioral changes register quickly.

Early-Stage Signs

Lethargy and isolation — Shrimp become less active than usual, stop grazing the substrate and hardscape, and tend to sit alone rather than congregating with the group. This is one of the most overlooked early signs because it can seem like normal resting behavior.

Washed-out coloration — Coloration becomes pale, translucent, or visibly faded compared to other shrimp of the same morph. Even a 20–30% reduction in color saturation is meaningful. Compare directly against a known-healthy tank mate.

Refusing food — Healthy shrimp almost always react to food being added to the tank. A shrimp that shows no response to a food it normally enjoys — or that approaches and then moves away — is worth watching closely.

Moderate-Stage Signs

Erratic or surface-seeking swimming — Darting randomly, swimming in circles, or repeatedly moving to the water surface may indicate neurological irritation from toxin buildup or oxygen-seeking behavior. This is a significant escalation from lethargy.

Clamped or tucked posture — Shrimp that curl tightly, hold their legs in, or hunch are physically stressed. This posture is also seen during a difficult molt, which can itself be a gateway to bacterial infection through exposed soft tissue.

White stringy feces — Internal gut bacteria imbalance produces pale, long, stringy waste instead of the compact dark fecal matter of a healthy shrimp. Often the first sign of internal opportunistic infection, and may accompany loss of appetite.^[3]

Serious / Late-Stage Signs

Reddish or pinkish discoloration — Red or pink patches on the body, especially around the head, near the gills, or along the tail fan, often indicate internal bacterial spread or early septicemia. This is not stress coloration — it is a medical emergency.

Milky or opaque body tissue — Normally translucent body tissue appearing white, cloudy, or opaque through the shell is a sign of systemic infection, protein denaturation, or muscle necrosis. Affected shrimp rarely recover without aggressive treatment.

Gill discoloration or swelling — Brown, black, or visibly enlarged gills near the shrimp's head indicate bacterial attack on respiratory tissue. Often accompanied by secondary fungal co-infection or gill flukes. Shrimp will typically struggle to breathe and seek high-flow areas.

Multiple deaths in a short window — Losing more than two or three shrimp in 24–48 hours, especially without obvious prior signs, indicates an aggressive fast-moving pathogen. Immediate action is required — bacterial loads in the water column will already be elevated.

Shrimp showing signs of bacterial infection with reddish discoloration

A shrimp infected with Micrococci bacteria — note the characteristic white/opaque muscle tissue visible through the translucent body. This internal opacity is a serious late-stage sign.^[9] Image: AquariumBreeder.com

API Freshwater Master Test Kit for ammonia nitrite nitrate pH testing

The API Freshwater Master Test Kit covers all the critical parameters — ammonia, nitrite, nitrate, and pH. Test the moment you notice behavioral changes; problems are almost always environmental first.

Common Pathogens to Know

While lab identification is rarely practical in the hobby, understanding the most common bacterial culprits helps you select the right treatment and anticipate how an infection may progress. In practice, most hobbyist treatments target gram-negative bacteria — which make up the vast majority of aquatic opportunistic pathogens.

Common bacterial pathogens in freshwater shrimp tanks and their typical presentations.

Pathogen	Typical Signs	Spread Risk	Key Notes
Aeromonas spp.	Reddening, rapid decline, hemorrhagic lesions, lethargy	Very High	Extremely common; thrives in warm, organically rich water. Most dangerous pathogen in the freshwater hobby.^[4]
Pseudomonas spp.	Gill damage, pale color, erratic swimming, surface ulcers	High	Highly opportunistic; often follows physical injury, failed molts, or crowding stress.
Flavobacterium columnare (Columnaris)	White-gray patches, tissue fraying, saddle-shaped lesions	High	More common in fish but transmissible in mixed tanks. Becomes significantly more aggressive above 77°F (25°C).^[5]
Mycobacterium spp.	Chronic wasting, hollow abdomen, gradual weight loss over weeks	Medium	Slow-progressing and resistant to most antibiotics. Also a zoonotic risk to humans with open skin wounds. Wear gloves.
Chitinolytic bacteria (Pseudomonas, Flavobacterium, Aeromonas, Vibrio)	Dark spot-like lesions on exoskeleton, erosion of carapace, progressing to internal spread	High	Also called "rust disease" or "shell disease." Bacteria produce chitinase enzymes that break down the carapace. Most dangerous at molt. Best treated with H₂O₂ in early stages.^[9]
Opportunistic gut bacteria	White/clear stringy feces, bloating, appetite loss	Low	Triggered by overfeeding, poor diet, or contaminated food. Rarely fatal on its own if caught early.

🧫 Zoonotic note: Mycobacterium marinum and some Aeromonas strains can infect humans through cuts or abrasions that come into contact with tank water. Always wash hands thoroughly after working in any aquarium. If you have open wounds or a compromised immune system, wear nitrile gloves.

Root Causes & Triggers

Pathogenic bacteria don't materialize suddenly — they exploit opportunity. The following are the most common conditions that allow bacterial populations to breach shrimp defenses. Addressing these is as important as treating the infection itself.

Poor Water Quality

Even brief spikes in ammonia or nitrite can measurably suppress shrimp immune function, creating a window for opportunistic bacteria. A 2019 review found that exposure to just 0.25 ppm of ammonia produced measurable immunosuppression in freshwater invertebrates.^[1] Keep parameters tightly controlled and test weekly even in established tanks.

Parameter	Target (Neocaridina)	Target (Caridina)	Notes
Ammonia	0 ppm	0 ppm	Any detectable amount is dangerous
Nitrite	0 ppm	0 ppm	As critical as ammonia
Nitrate	< 20 ppm	< 10 ppm	Lower is always better
pH	6.8 – 7.8	5.5 – 6.8	Stability matters more than exact value
Temperature	68 – 76°F	65 – 74°F	Higher temps accelerate bacterial growth
GH	6 – 8 °dGH	4 – 6 °dGH	Low GH = failed molts = infection entry points

Overfeeding & Organic Buildup

Uneaten food decomposes rapidly in a shrimp tank and creates pockets of high organic load — ideal breeding grounds for Aeromonas and anaerobic bacteria. Feed only what shrimp consume in 2–3 hours, remove uneaten food promptly with a turkey baster, and fast the tank entirely during active disease treatment.

Temperature Instability

Columnaris and many other pathogens become dramatically more virulent at temperatures above 77°F (25°C). More importantly, rapid temperature swings — even within a safe range — stress shrimp and suppress immune response. A heater malfunction or summer heat wave without adequate cooling is one of the most common triggers for outbreak events.

Skipping Quarantine

Introducing new shrimp, plants, snails, or hardscape directly to a display tank is one of the most common ways new pathogens enter. A clinically healthy shrimp can carry bacterial loads in its gut or on its surface that only manifest under the stress of shipping and rehoming. A minimum 2–4 week quarantine period in a separate established tank is non-negotiable for disease management.

Molting Stress & Crowding

A shrimp in the post-molt window is acutely vulnerable — its new shell is soft, it's largely immobile, and its surface is an easier entry point for bacteria. Failed molts caused by low GH or KH create open wounds on the body. Overcrowding compounds all of these risks by elevating baseline stress hormones across the entire population.

How Vibrio Enters the Body

Research into Vibrio transmission in shrimp has identified several entry pathways. Vibrio species can produce collagenase and chitinase enzymes that actively dissolve the chitinous shell — they don't simply wait for a wound. They preferentially penetrate between the thin chitin segments of the abdomen, spread along connective tissue fibers in muscle, and can cross the intestinal wall directly into the hemolymph ("blood") of weakened shrimp. Transmission via cannibalism of dead or dying tank mates is also well-documented — shrimp will eat deceased colony members, which is itself a stress-related behavior driven by overcrowding and inadequate feeding.^[8] This is another reason why removing dead shrimp immediately and maintaining a good protein component in the diet are critical prevention steps.

🔬 Germ counts matter: In healthy aquarium water, bacterial concentrations typically run 100,000–1,000,000 organisms per milliliter — versus roughly 10 per milliliter in drinking water. When organic load increases from uneaten food, waste, and dead animals, Vibrio populations can reach 500,000 colony-forming units per milliliter, creating an infection pressure that even healthy shrimp struggle to resist.^[8]

Treatment Protocol

Speed and sequence matter. Moving directly to medication without addressing environmental factors is the most common treatment mistake — and the most common reason infections return. Work through these steps in order.

Test your water immediately. Ammonia, nitrite, nitrate, pH, temperature. Document results. Almost every outbreak has an environmental contributing factor that must be corrected for treatment to hold.

Isolate visibly infected shrimp. Move shrimp showing redness, cloudiness, or severe lethargy to a quarantine tank with mature, cycled water. This slows spread and allows more aggressive treatment without risking your display tank's biofilter.

Perform a conservative water change. 20–30% with temperature-matched, conditioned water. Dilute bacterial load and improve water quality without shocking already-stressed shrimp. Do not do a massive water change — the parameter swing will add stress.

Boost aeration immediately. Add an airstone or increase surface agitation. Many pathogenic bacteria are facultative anaerobes that thrive in low-oxygen zones near substrate and decor. Strong oxygenation actively inhibits their growth.

Remove all food and detritus. Vacuum the substrate. Cut feeding entirely for 48–72 hours during active treatment. Shrimp can fast safely for days — feeding bacteria is the immediate risk.

Remove activated carbon from filters. Carbon will absorb and neutralize most medications. Remove it before dosing and replace it only after completing the full treatment course.

Administer appropriate treatment based on severity — see the Medications section below. For mild cases, H₂O₂ spot treatment or herbal options may be sufficient. Moderate to severe infections require antibacterial medication.

Monitor daily. Test water parameters every 24 hours. Medications can temporarily disrupt beneficial bacteria and cause ammonia spikes. Add bottled nitrifying bacteria (Fritz Turbo Start, Seachem Stability) if parameters shift. Complete the full treatment course even if shrimp appear to improve early.

Recovery phase. After completing treatment, re-seed gut bacteria by feeding a probiotic-enriched food from our Food & Supplements collection. Do a series of small water changes to remove medication residue. Hold the tank stable for at least 4 weeks before adding new shrimp.

Hydrogen Peroxide (H₂O₂) Treatment

Hydrogen peroxide is one of the most effective and underused tools available to shrimp keepers. It works by releasing oxygen radicals that disrupt bacterial cell membranes and destroy biofilm — and it breaks down harmlessly into water and oxygen within hours, leaving no harmful residue. It is particularly effective against surface bacterial infections, gill issues, and algae-associated bacterial buildup on plants and hardscape.^[6]

⚠️ H₂O₂ is powerful — use it carefully. Overdosing will harm shrimp and kill beneficial bacteria. Never dose without measuring. Use 3% pharmacy-grade hydrogen peroxide only (not stronger concentrations). Remove shrimp from the area being spot-treated if possible.

Tank Dosing (Water Column Treatment)

For mild bacterial infections in the water column or when treating an active tank, a low whole-tank dose of 1–1.5 ml of 3% H₂O₂ per 10 gallons can be used. Add slowly near a filter return for even distribution. Increase aeration during treatment — the oxygen released can temporarily spike dissolved oxygen. Observe shrimp closely for 30 minutes after dosing. Some erratic or hyperactive swimming immediately after dosing is normal — the rapid oxygen release from H₂O₂ breakdown is stimulating but not harmful at correct doses. However, if shrimp begin gasping at the surface or show signs of genuine distress beyond brief excitement, perform an immediate 30% water change. Do not repeat more than once every 48 hours.

Spot Treatment (Plants & Hardscape)

For bacterial or algae buildup on specific plants, substrate patches, or decorations, a targeted spot treatment is far safer than a whole-tank dose. Using a syringe or pipette, apply 1–2 ml of 3% H₂O₂ directly onto the affected area with the tank pump turned off. Allow 5 minutes of contact time, then resume flow. This method is especially effective against cyanobacteria mats, bacterial slime on leaves, and surface pathogens on new plants before introduction.

Plant Dip (Before Tank Introduction)

To sanitize new plants before adding them to a display tank, prepare a dip solution of 1–2 ml of 3% H₂O₂ per liter of water. Submerge plants for 5 minutes, then rinse thoroughly with clean water before planting. This kills surface bacteria, fungal spores, and many hitchhiking pests without significantly damaging most plant tissue. Delicate plants like mosses may show minor bleaching — use the lower end of the dose range.

💡 A note on concentration: Pharmacy-grade H₂O₂ is 3%. Some aquarium products contain higher concentrations — always verify and adjust dose accordingly. If you're unsure, use the lower end of any dose range. The consequences of underdosing are minor; the consequences of overdosing are not.

Medications & Treatment Options

Treatment selection should match the severity of the infection and how confident you are in the diagnosis. Always remove carbon from filters before medicating. Start with the least invasive option appropriate to the situation.

🍂 Indian Almond Leaves

Release tannins, flavonoids, and terpenes that create a mildly acidic, bacteriostatic environment. Best as ongoing prevention or very early intervention. Tints water amber. Can be used continuously without harm to shrimp. Shop Indian Almond Leaves →

🌰 Alder Cones

Similar to IAL — rich in tannins and organic acids with mild antibacterial properties. Slower to release, good for continuous long-term conditioning. Works synergistically with IAL for a combined effect. Shop Botanicals →

🌿 API Melafix

Tea tree oil–based treatment effective against mild surface bacterial infections and minor tissue damage. Use at half the label dose for shrimp — sensitivity has been reported at full dose. Not effective against systemic infections.

💊 Seachem KanaPlex

Kanamycin-based broad-spectrum antibiotic targeting gram-negative bacteria including Aeromonas and Pseudomonas. Can be dosed in water or mixed into food for internal infections. Will disrupt biofilter — monitor ammonia daily.

🔵 Seachem PolyGuard

Combination treatment targeting bacteria, fungi, and external parasites simultaneously. Useful when the cause is unclear or co-infections are suspected. Generally shrimp-safe at label doses. Good choice for early intervention when uncertain.

💉 Maracyn (Erythromycin)

Effective against gram-positive bacteria. Less commonly needed in shrimp tanks (most pathogens are gram-negative) but useful for persistent infections where gram-negative treatments have failed. Significant biofilter impact — use with care.

🧬 Antibiotic resistance: Completing the full treatment course is critical. Under-dosing or stopping early when shrimp appear to improve is the leading cause of antibiotic-resistant bacterial populations developing in home aquariums. If you start a course of antibiotics, finish it.^[7]

Prevention & Long-Term Tank Health

A stable, well-maintained tank with healthy, low-stress shrimp is a hostile environment for pathogenic bacteria. These practices significantly and measurably reduce outbreak risk.

Quarantine everything. New shrimp, snails, plants, and hardscape all go through a minimum 2–4 week quarantine in a separate tank before introduction to any display tank. No exceptions.

Feed sparingly. Only what shrimp can consume in 2–3 hours. Remove uneaten food with a turkey baster within that window. Hungry shrimp are healthier than shrimp in fouled water.

Small, consistent water changes. 10–20% weekly is far healthier than 50% monthly. Stability and consistency prevent the parameter swings that trigger stress-induced immune suppression.

Temperature control. Use a reliable heater with a separate thermometer to verify accuracy. Aim for the lower end of your species' safe range — cooler water slows bacterial metabolism and reduces outbreak severity.

Strong aeration. Maintain dissolved oxygen above 6 mg/L at all times. This is a meaningful passive defense against the anaerobic conditions that favor many dangerous pathogens.

Use Indian Almond Leaves and Alder Cones as continuous tank conditioners. Their tannins provide ongoing mild antibacterial support and closely replicate the natural leaf-litter environments shrimp thrive in.

Dip all new plants in a 1–2 ml/L H₂O₂ solution for 5 minutes and rinse before adding to any tank. This kills surface bacteria, fungal spores, and many pests without significantly harming plant tissue.

Maintain GH and KH appropriate for your species. Low GH means failed molts; failed molts mean open wounds; open wounds mean bacterial entry points. For Neocaridina, target 6–8 °dGH and 3–8 °dKH.

Avoid overstocking. A general guideline is 5–10 adult shrimp per gallon for Neocaridina. Overcrowded tanks have higher baseline stress, more organic waste, and faster outbreak propagation.

Keep a seeded sponge filter running in your display tank at all times so it stays colonized with beneficial bacteria. When you need a quarantine tank in a hurry, this seeded sponge provides an immediately cycled environment.

Never reuse equipment between tanks that has had a disease outbreak without sterilization. Rinse with a 1:20 bleach solution, then dechlorinate thoroughly and dry before use.

Test parameters weekly even when everything looks healthy. Slow creeping nitrate rises are one of the most common unnoticed contributors to chronic immune suppression in otherwise well-kept tanks.

Troubleshooting

Treatment didn't work and shrimp are still dying — Check whether you removed carbon from the filter before dosing; if not, the medication was absorbed and never reached therapeutic levels. Also confirm the medication targets gram-negative bacteria — most shrimp pathogens are gram-negative. Consider switching to KanaPlex if a broad-spectrum treatment failed.

Infection cleared but came back weeks later — The root environmental cause was not addressed. Bacteria don't disappear; they retreat to a manageable level when conditions improve. If the stressor remains — overfeeding, elevated nitrate, chronic temperature stress — they will rebound. Revisit water parameters and husbandry practices systematically.

One shrimp is clearly sick but the others look fine — Isolate the individual immediately. This is your window to act before spread. Early isolation and targeted quarantine-tank treatment gives the best odds of saving the individual and protecting the colony.

Redness appears but water parameters are perfect — Rule out copper first — it causes very similar reddening and rapid death. Check any medications, fertilizers, or tap water supplements for copper content. A single copper-based medication dose can be lethal to shrimp even at fish-safe concentrations.

Shrimp surviving but not recovering color or activity — Post-infection recovery can take 2–4 weeks. Support with high-quality food from our Food & Supplements collection, stable parameters, and botanicals. Avoid stressing recovering shrimp with additional water changes beyond routine maintenance.

White stringy feces but no other symptoms — This typically indicates an internal gut imbalance rather than a systemic infection. Fast for 48 hours, then re-introduce food with probiotic content from our Food & Supplements range. If it persists after a week, consider a low-dose KanaPlex food treatment targeting internal bacteria.

Shop Health & Prevention Supplies

🦐 All Neocaridina 🦐 Caridina Shrimp 🍂 Almond Leaves 🌿 All Botanicals 🪷 Lotus Pods 🍽️ Food & Supplements 🐚 Freshwater Snails 🪨 Hardscape 📋 Neocaridina Care Guide 🌊 Environment Setup Guide

Need Help With a Sick Tank?

Our team keeps shrimp and knows what you're going through. Reach out — we're happy to help troubleshoot, recommend treatment options, or just talk through what you're seeing. And when you're ready to restock after an outbreak, we've got healthy, well-conditioned Neocaridina and Caridina shrimp ready to go.

🦐 Shop Healthy Shrimp 🌿 Browse Botanicals

Sources & Citations

[1]Camargo, J.A. & Alonso, Á. (2006). Ecological and toxicological effects of inorganic nitrogen pollution in aquatic ecosystems. Environment International, 32(6), 831–849. Ammonia immunosuppression in freshwater invertebrates. doi.org/10.1016/j.envint.2006.05.002
[2]Austin, B. & Austin, D.A. (2016). Bacterial Fish Pathogens: Disease of Farmed and Wild Fish (6th ed.). Springer. Opportunistic pathogen behavior, secondary infection mechanisms in crustaceans.
[3]Tzuc, J.T. et al. (2014). Microbiota from Litopenaeus vannamei: digestive tract microbial community of Pacific white shrimp. SpringerPlus, 3(1), 280. Gut bacterial imbalance, fecal indicators of dysbiosis in shrimp. doi.org/10.1186/2193-1801-3-280
[4]Eddy, S.D. & Jones, S.H. (2002). Microbiology of summer flounder Paralichthys dentatus fingerling production at a marine fish hatchery. Aquaculture, 211(1–4), 9–28. Aeromonas prevalence and pathogenicity in aquaculture systems.
[5]Suomalainen, L.R. et al. (2005). Columnaris disease in salmonid fish: temperature effects and the role of virulence. Diseases of Aquatic Organisms, 65(3), 235–242. Temperature-virulence relationship in Flavobacterium columnare. doi.org/10.3354/dao065235
[6]Rach, J.J. et al. (1997). Effect of hydrogen peroxide on parasites and fish. Journal of Aquatic Animal Health, 9(2), 118–128. H₂O₂ mechanism of action, dosing, and shrimp safety. See also: Shrimpybusiness.com. Freshwater Shrimp Diseases & How to Treat Them. shrimpybusiness.com
[7]Cabello, F.C. (2006). Heavy use of prophylactic antibiotics in aquaculture: a growing problem for human and animal health and for the environment. Environmental Microbiology, 8(7), 1137–1144. Antibiotic resistance development from incomplete treatment courses. doi.org/10.1111/j.1462-2920.2006.01054.x
[8]Garnelio.de (2016). Shrimp die for no reason! #Shrimp diseases. Vibrio spp. transmission pathways, chitin-dissolving enzymes, organic load germ counts, immune-weakening factors. garnelio.de. See also video resources: YouTube — youtube.com/watch?v=KfRyMg1VarM; youtube.com/watch?v=T-UjbfGBJ7o; youtube.com/watch?v=9Z2k0N870KE
[9]Shrimpybusiness.com (2023). Freshwater Shrimp Diseases & How to Treat Them. Chitinolytic bacterial disease (rust/shell disease), chitinase enzyme mechanism, H₂O₂ treatment protocol. shrimpybusiness.com. See also: AquariumBreeder.com. Understanding Dwarf Shrimp Diseases and Parasites. aquariumbreeder.com
[10]Chandrakala, D. & Priya, R. (2017). Vibriosis in shrimp aquaculture. In: Arunachalam, M. et al. (eds). Cited in: Frontiers in Marine Science (2024). Microbes and pathogens associated with shrimps. doi.org/10.3389/fmars.2024.1397708

Sign In

Bacterial Infections in Shrimp Tanks