Possible cyanobacteria in a shrimp tank: observe, remove and check

Carefully remove accessible slime mats, check filtration and gas exchange, and investigate recent changes. Blue-green colour, musty smell or a peeling sheet can be a clue, but identifies neither the organism nor a toxin. Treat deteriorating shrimp promptly as a health and water-quality problem.

What “blue-green algae” means

Cyanobacteria are photosynthetic bacteria. Some can produce toxins; that does not establish toxicity in every visible mat. Heavy growth and decomposition can also affect oxygen conditions. The EPA source concerns water bodies, not a safe dose or treatment for dwarf shrimp.

A traceable first response

1. Record spread and recent changes with photographs and a timeline.
2. Selectively siphon loose mats and accumulated debris. Check waste water for juveniles and prepare suitable replacement water.
3. Restore obstructed circulation and access to the water surface. Remove clearly decaying material.
4. Check temperature, ammonia/nitrite and oxygen where indicated. Review lighting, fertiliser and leftovers together.
5. Compare recurrence in the same place. If growth rapidly returns or animals deteriorate, seek targeted help with photographs, readings and product names.

A complete blackout, antibiotic or algaecide is not a neutral first step: it changes the system and can affect decomposition and animals. Without dependable identification and suitable product guidance we provide no dosing recipe. Distressed animals cannot wait for an algae experiment; use the problem-solving route.

Sources and scope

• US EPA: Cyanobacteria and cyanotoxins
• Aqueon: Prevention and control of nuisance algae
• UF/IFAS: Dissolved Oxygen for Fish Production
• UF/IFAS: Ammonia in Aquatic Systems

EPA describes cyanobacteria and possible oxygen and toxin effects in natural waters. This does not establish toxin production in your aquarium. The first maintenance steps are editorial guidance, not laboratory identification or a validated treatment.