Green growth beneath a shrimp: eggs or Cladogonium?
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The name “green fungus” is often used for an irregular green growth beneath freshwater shrimp. One documented organism associated with such growth is Cladogonium, a green alga rather than a fungus. Green eggs are another possibility. Colour alone does not establish a diagnosis, and a photograph cannot reliably distinguish every organism.
Eggs or an unusual growth?
| What you see | What it suggests | Next check |
|---|---|---|
| Separate, rounded eggs held together under the abdomen | A berried female; egg colour can vary | Look for repeated smooth shapes and normal tending or fanning. |
| Irregular threads, tufts or branching material around the underside | A suspicious attached growth | Take clear side and underside photographs without handling the shrimp unnecessarily. |
| A patch visible only through the body, with no clear attached structure | Colour alone is inconclusive | Observe shape and location under better lighting before labelling it disease. |
A female can fan her swimmerets in more than one situation, so movement alone is not diagnostic either. Do not scrape the underside to test what is attached. Compare the structure with normal berried-shrimp care, while treating any uncertain identification cautiously.
What is known about Cladogonium?
Bauer and colleagues’ 2021 investigation documented Cladogonium on imported freshwater shrimp during an outbreak involving several health problems. This supports taking an attached green growth seriously, but it does not show that every green patch has the same cause or that the alga alone explains every death.
Hobby discussions sometimes use names such as Ellobiopsidae and Cladogonium interchangeably. They should not be treated as confirmed identifications from colour or a seller's label. Microscopy and a knowledgeable assessment may be needed to identify the organism and distinguish it from other attached material.
What to do when the growth looks suspicious
- Document what you can see. Record when it appeared, recent additions, feeding response and whether other shrimp are affected. Take sharp images from more than one angle.
- Check basic water quality. Test ammonia and nitrite, and review temperature, aeration and recent changes. An attached growth does not rule out a separate water-quality problem.
- Assess a suitable isolation setup. A mature quarantine tank with matched water and adequate aeration is preferable to an unfiltered jar. Avoid repeated chasing or transferring the animal into worse conditions.
- Keep equipment separate. Do not move quarantine water, nets or other wet equipment between tanks without an appropriate process for the specific contamination risk; rinsing or drying alone does not establish disinfection.
- Seek qualified help if the condition worsens. Repeated deaths, several affected animals or uncertainty about treatment warrant advice from an aquatic veterinarian or aquatic-health professional.
Use the isolation guide to plan the receiving tank and the biosecurity checklist to reduce avoidable transfer between aquariums. Quarantine improves separation and observation; it is not itself a proven cure.
Why this guide does not give a universal treatment recipe
There is no treatment that can be selected responsibly from the phrase “green fungus” alone. Internet reports of salt dips, dyes or aquarium medicines are not interchangeable evidence of a safe, effective protocol for your shrimp, diagnosis and tank.
Do not combine treatments, calculate a dose from an unidentified product or medicate a whole colony before checking suitability for invertebrates and the biological filter. A product advertised for fish is not automatically safe for shrimp. Review medication safety and obtain diagnosis-specific advice before treatment.
What to monitor afterwards
Keep photographs under similar lighting so that changes in shape are easier to compare. Note grazing, activity, molts, water readings and any new cases. A cleaner-looking underside after a molt is an observation, not proof that the problem cannot return.
Do not return an animal to a colony merely because a single photograph looks better. Base the decision on continued observation, the suspected diagnosis and any professional treatment advice. If more animals develop signs, reconsider the source and shared conditions rather than assuming every case needs the same chemical response.
Sources and scope
- Bauer et al. (2021): Cladogonium in a multifactorial disease outbreak
- Maciaszek et al. (2023): Epibiont cohabitation in Neocaridina davidi
- UF/IFAS: Cherry shrimp, Neocaridina davidi
- UF/IFAS: Fish Health Management Considerations in Recirculating Aquaculture Systems
The studies were assessed through author abstracts, with figure captions also reviewed for the 2023 paper. They document growth on Neocaridina davidi but supply no universal home treatment. The comparison table and follow-up steps are editorial aids.
