Cyanobacteria (Red Slime) is a common aquarium disease/pest affecting reef + freshwater. Recognizing it early and treating quickly is the difference between losing a single fish and losing an entire tank.
Symptoms to watch for
red/maroon slime sheet on substrate. Watch for behavior changes (reclusive, refusing food, color loss) as early warning signs - even before visible symptoms appear, fish stress patterns indicate something is wrong.
Treatment protocol
ChemiClean, address phosphate + flow + lighting. Always treat in a separate hospital tank to protect invertebrates, coral, and beneficial bacteria. Follow medication protocol exactly - underdosing produces resistance, overdosing creates new problems.
Prevention
Quarantine new fish for 4-6 weeks before adding to your display tank. Stable parameters + appropriate stocking + adequate filtration prevent the chronic stress that makes fish susceptible to disease in the first place.
When to escalate
If symptoms persist beyond expected treatment duration, parasites/symptoms reappear after treatment, or the disease spreads despite isolation, escalate to a fish-specific veterinarian or experienced reef keeper. Aquatic veterinarians offer prescription medications (chloroquine, levamisole) not available over-the-counter.
Cyanobacteria (Red Slime) FAQ
Is cyanobacteria (red slime) contagious?
Pests can spread between corals; isolate infested specimens immediately.
Can I treat in the display tank?
For most diseases - no. Copper kills inverts, antibiotics destroy beneficial bacteria. Always treat in a hospital tank.