Overview
Acropora Red Bugs (Tegastes acroporanus) are tiny parasitic copepods that live on Acropora corals. They’re one of those pests that can absolutely wreck your SPS vibe without looking dramatic at first. You don’t usually see “a bug problem.” You see Acros that stop looking happy: less polyp extension, dull color, stalled growth, and that general “something’s off” feeling that makes you start checking alkalinity five times a day.
Red bugs are small, but they’re persistent. They irritate Acropora by living and feeding on the coral’s surface, and over time that stress can cause slow decline—especially in already-stressed systems or sensitive acros.
If you keep Acropora and trade frags, red bugs are one of the reasons serious SPS keepers develop strict intake habits.
Quick Care Snapshot
Common Name: Acropora Red Bugs / Red Bugs
Scientific Name: Tegastes acroporanus
Reef Safe: No (parasite/pest on Acropora)
Difficulty: Easy to introduce, annoying to eliminate
Target Host: Acropora spp. (primary)
Where They Live: On Acropora skin and around polyp areas
Primary Signs: Reduced polyp extension, dull color, stalled growth, chronic irritation
Visibility: Tiny — often seen as yellow/orange dots with a magnifier
Main Risk: Spreads via Acropora frag transfers
Natural Background
Tegastes copepods exist in marine environments, and many are part of the normal “microfauna” world. Tegastes acroporanus is different because it’s strongly associated with Acropora in captivity and behaves like a parasite/irritant on the coral.
In nature, there are usually more predators and more space. In our tanks, Acropora colonies are concentrated, and the pests can hop from coral to coral with ease—especially when we’re constantly moving frags around.
Tank Requirements
Red bugs don’t require special tank parameters. If you can keep Acropora alive, you can support red bugs.
They tend to become a problem when:
• New Acropora is added without strict inspection habits
• SPS are already stressed (swingy alk, unstable nutrients, harsh lighting changes)
• There aren’t enough natural “micro-predators” in the system to apply pressure
• The infestation grows unchecked long enough to affect multiple colonies
Where to look
• On Acropora branches, especially near polyps
• On smooth-skinned Acros, they can be easier to spot
• Around the base and shaded sides (anywhere the coral is less actively “cleaned” by flow)
Feeding
Red bugs feed on the coral’s surface/secretions and irritate the tissue. You don’t “feed” them like you feed a snail. They’re living off the Acropora itself.
That’s why nutrient control isn’t the solution:
• Lower nutrients may make Acros more sensitive
• Higher nutrients may mask symptoms by making corals look “fuller”
But neither removes the pest.
Compatibility
With corals
• Acropora: Primary target. This is an Acro problem.
• Other SPS: Usually not the main target in the same way, but they can hitchhike and be present in the system.
With fish/inverts
Most fish won’t make a noticeable dent. Some wrasses and small predators may pick at microfauna, but relying on that is unpredictable. Red bugs can still persist and spread.
The real compatibility takeaway
Red bugs are “compatible” with your reef in the worst way: they can live in it for a long time while slowly damaging the coral you care about most.
Common Mistakes
1) Thinking it’s an alkalinity or lighting problem first (every time)
If your Acros suddenly lose polyp extension and look irritated, parameters absolutely matter—but red bugs should be on the short list, especially if you’ve added frags recently.
2) Not using magnification
Red bugs are tiny. If you’re trying to identify them with bare eyes from across the room, you’re going to miss them.
3) Assuming “they’re always obvious”
They’re not. Many outbreaks are low-grade but chronic. The coral looks meh for weeks, and you keep tweaking the tank thinking it’s “SPS being SPS.”
4) Treating one coral like it’s an isolated issue
If one Acro has them, assume:
• others have been exposed
• the pest exists in the system, not just that frag
5) Ignoring intake habits
Almost every red bug story starts with: “I added a frag.”
Notes & Variations
What do they look like?
Hobbyists often describe them as:
• Tiny yellow/orange specks
• Concentrated around polyp areas
• Visible with a magnifying glass or macro camera
• Often easiest to see on lighter-colored Acros
Symptom pattern
• Polyp extension reduced (especially daytime PE)
• Coral looks “dry” or irritated
• Growth slows
• Color dulls
• Some colonies look worse than others even in the same tank
Don’t confuse with “normal” microfauna
Lots of copepods and tiny critters are good. Red bugs are different because they show up on Acropora tissue and correlate with chronic irritation.
Final Thoughts
Red bugs are one of those SPS pests that teach the same lesson as AEFW: your reef can be stable and your parameters can be perfect, and you can still lose momentum if a pest gets established.
The good news is that they’re not mystical. They’re a specific organism with a specific host, and the symptoms are consistent once you learn them. The bad news is they spread easily through frag culture.