Red Planaria and Reef Flatworms

Overview

What It Is: “Red planaria” is a hobby name often applied to rust-colored acoels such as Convolutriloba species, which are not true planarians. “Reef flatworms” also includes unrelated marine flatworms, including coral-feeding polyclads such as the Acropora-eating flatworm Prosthiostomum acroporae (formerly Amakusaplana acroporae).

Why It Matters: Different flatworms have different diets, hosts, eggs, risks, and treatment responses. A dense red acoel population may mainly shade or irritate coral, whereas a coral-eating flatworm can remove living tissue. Misidentification can delay effective control or expose the reef to unnecessary treatment.

When It May Be Normal or Temporary: A few unidentified flatworms away from coral may cause no visible harm. Some harmless or beneficial flatworms occur in marine systems. Monitor until feeding damage, rapid multiplication, or a reliable identification is established.

When It Indicates a Real Problem: Numbers increase, mats form on lit surfaces, coral remains covered or retracted, fresh feeding scars appear, tissue disappears from a particular coral group, egg clusters recur, or livestock becomes distressed during a die-off.

Aquarium Types Where It Commonly Appears: Reef displays, coral quarantine tanks, frag systems, aquaculture systems, fish-only-with-live-rock tanks, sumps, refugiums, and aquariums receiving coral or mature live rock.

Livestock or Systems Most at Risk: Acropora collections, recently imported coral, dense frag systems, nano reefs, tanks with weak export or aeration, and systems with a large hidden population that may die simultaneously.

Where It Occurs

Saltwater and reef aquariums, especially coral displays, frag systems, and quarantine tanks.

What Can Be Affected

Dense red acoels can cover rock, glass, sand, and coral, reducing light and irritating tissue. Coral-feeding flatworms can remove tissue from Acropora or other host corals. Fish and invertebrates may be harmed indirectly if many flatworms die at once.

When to Act

Low to moderate for a small non-coral-feeding population. High when numbers are dense, coral tissue is being consumed, or a whole-tank treatment could cause a mass die-off. Emergency signs include fish distress, low oxygen, or ammonia after treatment or die-off.

Why It Matters

Flatworms commonly arrive on coral or live rock, and correct identification changes the control plan.

Signs & Identification

Visible Signs: Rust-red, orange, tan, white, or mottled flattened animals gliding on surfaces; dense patches in light; coral-colored worms on branches or undersides; oval feeding marks; pale tissue loss; reduced polyp extension; and small egg clusters on exposed skeleton or plug material.

Livestock Behavior Signs: Affected coral may retract, pale, collect mucus, or lose tissue. Fish may behave normally until treatment or mass die-off, when rapid breathing, surface gasping, hiding, loss of balance, or sudden death requires immediate stabilization.

Water-Test or Instrument Findings: No standard aquarium test identifies flatworms. Ammonia may rise and dissolved oxygen may fall after a large die-off. Nitrate and phosphate can accompany excess food and detritus but do not prove that flatworms are present or identify the species.

Equipment or Flow Findings: Red acoels often concentrate in illuminated, lower-flow zones but can occur throughout the system. Fine siphon tubing, filter socks, skimming, fresh carbon, and strong aeration help export animals and treatment byproducts. Flatworms may hide in racks, plumbing, and sump surfaces.

Odor, Texture, Color, Location, or Pattern: Flatworms are thin, soft, and glide rather than crawl on jointed legs. Common red acoels are rust to reddish brown and may have a forked or lobed rear margin. Coral-eating flatworms can match coral color and are often found on shaded branch surfaces or near fresh feeding damage.

Typical Onset and Progression: A few hitchhikers may remain unnoticed before rapid asexual or sexual reproduction makes the population visible. Coral-eating forms may be discovered only after repeated bite marks, declining polyp extension, or egg clusters appear.

How to Confirm the Problem: Use non-invasive magnification and clear photographs to document movement, body shape, host and suspected eggs. Examine a safely removable non-zoanthid host only without damaging tissue. Refer zoanthid/Palythoa or encrusted-base intervention rather than cutting, scraping or blasting it.

What Cannot Be Confirmed Visually: Color alone cannot confirm species, toxicity, diet, treatment sensitivity, or whether every coral lesion was caused by the observed worm. A dip may reveal mobile adults but does not prove that eggs are absent.

What It Looks Like: Small, soft, flattened animals gliding over glass, rock, sand, or coral. Common red acoels are rust, red-brown, or orange and may gather in lit, low-flow areas. Coral-eating flatworms can be pale, mottled, and difficult to see against their host; feeding scars and egg clusters may be easier to find.

Similar Problems / Differential Identification

Commonly Confused With: Copepods, amphipods, nudibranchs, slugs, polyclad worms, harmless acoels, fish lice, leeches, detritus worms, coral mucus, tissue sloughing, bleaching, red bugs, and other coral pests.

How Similar Problem 1 Differs: Copepods and amphipods have segmented bodies and visible legs and usually dart or crawl. Flatworms are unsegmented, leaf-like, and move with a smooth gliding motion.

How Similar Problem 2 Differs: Red acoels commonly gather on rock, sand, glass, and light-exposed coral without leaving host-specific bite marks. Acropora-eating flatworms remain closely associated with Acropora, camouflage against tissue, and produce feeding scars and eggs on dead skeleton or nearby hard surfaces.

Tests or Observations That Distinguish Them: Compare movement, body outline, color under white light, population pattern, coral host, feeding scars, and egg location. Inspect at night and during daylight, photograph through magnification, and examine a removed coral in a separate container.

Information Needed Before Recommending Treatment: Tank volume and age; fish, coral, and invertebrate list; photos or video; suspected species; affected host; number and distribution; eggs or feeding marks; recent additions; water parameters; prior dips or medication; and available carbon, saltwater, aeration, and quarantine space.

Urgency & Triage

Emergency Warning Signs: Surface gasping, rapid gill movement, loss of balance, widespread coral mucus, sudden polyp collapse, cloudy water, strong odor, low dissolved oxygen, detectable ammonia, or livestock death during or after a flatworm die-off or treatment.

Immediate Stabilization Steps: Stop the suspected treatment, maintain safe aeration and circulation, test water and record the product and amount. Capture accessible dead worms without damaging coral. Follow the exact product's emergency/export instructions or obtain reef-professional help for carbon and matched-water changes; equipment timing is not interchangeable between products.

Whether Feeding, Lighting, Dosing, or Equipment Should Be Paused: Pause flatworm medication and optional dosing during distress. Reduce feeding temporarily if ammonia or oxygen is a concern. Keep heat, circulation, skimming, mechanical filtration, and aeration operating unless the product instructions specifically require a controlled change.

Whether Isolation or Quarantine Is Appropriate: Use stable separate observation for an intact removable host when safe. Dip and egg intervention must match the identified organism, coral and exact formulation. Refer zoanthid/Palythoa tissue or encrusted-base work; do not prescribe universal egg scraping.

When Monitoring Is Safer Than Immediate Intervention: Monitor a few unidentified worms away from coral when no damage or growth is evident and treatment would pose greater risk. Photograph and count them while confirming whether they are multiplying or associated with a host.

Escalation Point: Escalate when the population grows quickly, coral tissue loss or eggs are present, several colonies are affected, siphoning cannot keep pace, or a chemical treatment is being considered for a dense whole-tank population.

Immediate Risk: Dense flatworms can shade or irritate coral, while coral-eating species can cause direct tissue loss. Killing a large population rapidly may release organic material and defensive compounds, reduce oxygen, raise ammonia, and stress fish and invertebrates.

Causes & Contributing Factors

Primary Cause: Introduction of flatworms or their eggs on wet aquarium material, followed by survival and reproduction in the receiving system.

Other Common Causes: Unquarantined coral and plugs, missed eggs, shared tools or water, repeated additions from an infested system, abundant microorganisms or detritus, and failure to repeat inspection after the first removal.

Water-Quality Factors: Excess suspended food and detritus may support some populations, but flatworms are not a direct water-quality test. Unstable salinity, temperature, pH, alkalinity, low oxygen, or ammonia can magnify coral and fish stress during control.

Biological or Pathogen Factors: Acoels and coral-feeding polyclads are different groups. Prosthiostomum acroporae lays egg batches on Acropora; that biology does not establish the reproductive stages or treatment schedule of every red hobby flatworm. Hidden stages can make a clean-looking tank misleading.

Algae or Pest Factors: Algae and biofilm can hide small worms and egg clusters. Red acoels may congregate where light supports their symbiotic algae. Other pests, including red bugs, nudibranchs, and snails, can cause similar coral damage and may coexist.

Equipment or Flow Factors: Low-flow pockets can collect red acoels and detritus, but increasing flow alone rarely eradicates them. Weak skimming, exhausted carbon, limited mechanical filtration, or inadequate aeration increases risk during a die-off.

Feeding, Stocking, or Husbandry Factors: Heavy feeding can increase suspended and benthic food, while crowded coral racks make inspection difficult. Predator additions can create new compatibility and feeding obligations without eliminating eggs or hidden worms.

Maintenance Factors: Skipping plug and coral-base inspection, transferring shared water, reusing contaminated tools, failing to siphon before treatment, leaving egg clusters, and stopping follow-up too soon allow recurrence.

Recent Changes That Can Trigger It: New coral, plugs, live rock, macroalgae, rubble, shared tools, increased feeding, reduced flow or filtration, coral relocation, or a treatment that kills many previously hidden worms.

Environmental or Seasonal Factors: Aquarium populations can expand when light, food, temperature, and host availability favor reproduction. A sudden visible outbreak often reflects earlier unnoticed reproduction rather than spontaneous appearance.

Diagnostic Workflow

Questions to Ask About Recent History: What was added and when? Where were the first worms seen? Are they on one coral genus or many surfaces? Are there bite marks or eggs? Has feeding, flow, or filtration changed? Was any medication used, and did livestock react?

Step 1 - Immediate Visual Inspection: Inspect glass, sand, rock, shaded crevices, coral branches, undersides, bases, plugs, racks, and sump surfaces under white light and magnification. Record the host, body shape, movement, damage, and eggs.

Step 2 - Water Tests and Measurements: Measure temperature and salinity. Check ammonia and dissolved oxygen when the population is dense, a die-off occurred, or animals are distressed. Record pH, alkalinity, nitrate, and phosphate to assess coral stability and husbandry.

Step 3 - Equipment and Flow Checks: Verify circulation, surface agitation, skimmer function, clean mechanical media, and available fresh carbon. Identify low-flow collection areas and confirm that emergency water-change equipment is ready before treatment.

Step 4 - Livestock, Plant, or Coral Checks: Compare affected and unaffected coral for polyp extension, coloration, bite marks, exposed skeleton, mucus, eggs, and tissue recession. Check fish breathing and invertebrate behavior before and after intervention.

Step 5 - Narrowing the Cause: Separate widespread red acoels from host-specific coral feeders, rule out other coral pests and unstable water, estimate the hidden population, and determine whether removal must address adults, eggs, or both.

Common Diagnostic Mistakes: Calling every flatworm red planaria, relying on color alone, missing camouflaged adults and eggs, assuming a dip kills eggs, treating coral damage without checking parameters, and confusing post-treatment toxicity with the original infestation.

First Checks: Photograph the animal and its movement; note color, shape, size, location, and host coral; inspect coral undersides and bare skeleton for bite marks or eggs; estimate population density; and check temperature, salinity, oxygen, ammonia, and coral condition.

Correction & Management

Immediate Stabilization: Maintain safe oxygenation and water quality, stop harmful dosing and capture accessible dead worms without disturbing coral. Use the exact product or professional plan for filtration, carbon and matched-water changes; do not substitute a generic neutralization procedure.

Cause-Specific Correction: For a confirmed nuisance red-acoel population, use repeated controlled siphoning and waste review. For suspected coral-feeding polyclads, isolate the affected host when safe and obtain a coral-specific control plan that addresses observed adults and eggs. Do not transfer a red-acoel whole-tank product or assume a dip kills eggs; dip choice and any repeat schedule require evidence for the organism, coral and formulation.

Recommended Order of Actions: 1) Identify group and host. 2) Assess water and livestock. 3) Collect accessible free-living worms without crushing them. 4) Isolate an intact affected host only when safe. 5) Obtain a host-specific adult-and-egg plan, referring hazardous tissue work. 6) Prepare label-specific export and monitoring. 7) Use only an exact compatible intended-use product if justified. 8) Repeat observation without assuming eradication.

Water-Change Guidance if Applicable: Prepare enough temperature- and salinity-matched saltwater before chemical control. Siphon worms and debris during changes. Follow the product label, and use additional changes when ammonia, low oxygen, cloudiness, odor, or livestock distress indicates poor water quality.

Equipment or Filtration Changes: Capture siphoned worms outside the display and service mechanical media without damaging biofiltration. Filtration, skimmer and carbon timing must follow the exact product or professional plan. Salifert's Flatworm eXit instructions remove carbon initially and introduce it when worms die; do not convert that timing into a rule for other products.

Maintenance Changes: Inspect and document accessible free-living worms, host bases and suspected eggs non-invasively; keep quarantine tools separate. Do not remove encrusted plug material by cutting or scraping living tissue. Refer hazardous or inseparable host intervention.

Livestock, Plant, or Coral Care: Maintain host-appropriate conditions and minimize handling. A safely removable non-zoanthid host may have a dip only under the exact compatible label or qualified plan, including any rinse. Do not scrub, cut or scrape zoanthid/Palythoa tissue or an encrusted base.

Treatment or Medication Considerations if Applicable: Salifert's Flatworm eXit manufacturer page warns about dying flatworms' body fluids and requires preparatory siphoning and product-specific export. This supports that product's precautions, not universal reef safety, Acropora-eating-flatworm efficacy or egg eradication. Follow the current complete package label; do not reproduce or extrapolate its dose or use it for another pest group without evidence.

Expected Time to Improvement: Visible counts can change without hidden stages being controlled. Recheck the identified group, host damage and suspected egg sites; follow a host-specific professional plan or exact label rather than a universal weeks-long treatment calendar.

Signs the Correction Is Working: Counts decline between inspections, no new egg clusters or bite marks appear, coral extension and tissue margins stabilize, siphoning yields fewer worms, and fish and invertebrates remain normal after each intervention.

Signs the Problem Is Worsening: Flatworms spread to new surfaces or hosts, eggs recur, feeding scars expand, coral loses tissue, mats form, or fish and invertebrates show respiratory or behavioral distress during a die-off.

What to Do if the First Correction Fails: Reconfirm the group and affected hosts, record hidden sites and suspected eggs, and review the exact label with a reef or coral-health professional. Do not escalate doses, use a different pest's product, or improvise tissue scraping when control fails.

Safest First Action: Siphon visible flatworms through fine tubing into a removable filter or discard container, reducing the population gradually without crushing them. Isolate affected coral when practical, confirm the type of flatworm, and prepare fresh saltwater, activated carbon, aeration, and mechanical filtration before any broader treatment.

Things Not To Do

Unsafe Shortcut: Dosing a dense infestation immediately without first siphoning worms or preparing for a mass die-off.

Why It Is Risky: Salifert warns that its target flatworms' body fluids released on death may be toxic. A large die-off can also burden water quality. This does not establish the same toxin or severity in every flatworm group; follow the exact compatible product's preparatory and export instructions.

Safer Alternative: Reduce the population mechanically in stages, identify whether coral hosts and eggs require separate control, and have matched saltwater, fresh carbon, mechanical filtration, aeration, and monitoring ready before any labeled treatment.

Products or Treatments Commonly Misused: Unlabeled dewormers, livestock medications, copper, pesticides, oxidizers, concentrated peroxide, freshwater exposure for saltwater livestock, excessive dip strength or time, whole-tank coral dips, and predator additions treated as guaranteed cures.

What Not to Do: Do not assume every flatworm is red planaria, medicate before identifying the host and population, kill a dense infestation all at once without export capacity, rely on predators as a guaranteed cure, or dip coral without checking species tolerance and removing eggs.

System-Specific Considerations

Freshwater Aquariums: Not applicable to this marine problem. Freshwater planaria and leeches require different identification, livestock-safety precautions, and treatments.

Planted Aquariums: Not applicable. Do not transfer reef-flatworm treatments to planted freshwater aquariums.

Saltwater Fish-Only Aquariums: Red acoels may occur on rock and glass even without coral. Confirm the organism, control dense populations gradually, and protect fish from low oxygen, ammonia, and treatment byproducts.

Reef Aquariums: Separate free-living nuisance acoels from host-associated coral feeders. Use appropriate separate observation, accessible controlled collection and stable reef care. Egg intervention must be host-specific; refer zoanthid/Palythoa and encrusted-base work rather than performing consumer scraping.

Nano Aquariums: Small water volume increases the effect of medication, toxins, oxygen loss, and ammonia. Remove worms gradually, measure products precisely, prepare a large matched-water reserve, and monitor livestock continuously.

New Aquariums: Inspect and quarantine every coral and wet hard surface before placement. Early removal is easier, but preserve biological filtration and avoid treating an immature system without a confirmed need.

Mature Aquariums: Large colonies and established rockwork can hide adults and eggs. Use a staged plan, protect old coral colonies and biofiltration, and expect repeated inspection rather than a single corrective event.

Ponds or Outdoor Systems: Not applicable. Do not release marine flatworms, coral, aquarium water, medication, or treatment waste into ponds, storm drains, beaches, or natural waterways.

Safety & Sensitivities

Fish Safety: Fish are usually harmed indirectly by treatment, low oxygen, ammonia, or mass die-off rather than by the flatworms themselves. Watch breathing closely, maintain aeration, and move fish only when a stable prepared system is available.

Freshwater Invertebrate Safety: Not applicable to the reef system. Products and doses used for freshwater planaria may be unsafe or ineffective for marine flatworms and reef invertebrates.

Coral and Saltwater Invertebrate Safety: Dip and whole-tank-product compatibility varies. Do not assume a manufacturer's safety claim covers every resident or a different pest group. A safely removable non-zoanthid host needs an exact-label or qualified plan; zoanthid/Palythoa egg or encrusted-base intervention is referred.

Plant Safety: Marine macroalgae can carry flatworms or eggs on holdfasts and attached rubble. Quarantine and inspect it, and do not use a dip that is untested for the algae or other desired organisms.

Medication and Chemical Risks: Chemical control can stress or kill non-target invertebrates and trigger a large flatworm die-off. Dose errors, retained residues, poor aeration, and inadequate export increase risk. Never combine treatments unless the labels and a qualified professional support it.

Copper Sensitivity: Do not use copper as a reef-flatworm treatment. It can harm marine invertebrates; no reef-safe concentration or safe future return interval is supplied.

Electrical, Heat, Leak, or Pressure Risks: Keep electrical connections dry, use GFCI protection and drip loops, unplug equipment before servicing it, and restore heat and circulation promptly. Secure siphon and water-change hoses to prevent spills and unintended drainage.

Human and Pet Safety: Follow exact product exposure warnings, avoid mouth-siphoning and keep chemicals and removed material away from children and pets. PPE does not make hazardous-coral work safe. Do not scrape, cut, scrub, heat or aerosolize zoanthid/Palythoa tissue or its encrusted base; obtain specialist handling advice and seek Poison Control or medical help after suspected exposure.

Situations Requiring a Veterinarian, Laboratory Test, Electrician, or Other Specialist: Aquatic veterinarian for fish distress or unexplained deaths; coral or reef specialist for host-specific infestations and valuable colonies; taxonomic or microscopy help for uncertain identification; electrician for wet equipment; and poison-control or medical advice after significant exposure.

When to Get Help: Use an experienced reef professional for dense infestations, valuable coral colonies, uncertain identification, or whole-tank treatment planning. Seek an aquatic veterinarian or emergency aquarium specialist if fish gasp, collapse, or show neurologic signs after a die-off or chemical exposure.

Prevention

Routine Prevention: Inspect wet additions under white light, use suitable separate observation, dedicate tools and prevent water transfer. Isolate an intact removable item only when safe; do not cut or strip an encrusted base as a routine plug-removal method.

Water-Testing Schedule: Track salinity, temperature, pH, alkalinity, nitrate, and phosphate on the reef’s normal schedule. Check ammonia and dissolved oxygen before and after a large treatment or die-off and whenever livestock shows respiratory distress.

Maintenance Practices: Inspect coral bases and undersides, siphon detritus and visible worms, clean racks and tools, change mechanical media, keep fresh carbon and mixed saltwater available, and record worm counts, egg locations, and coral damage.

Quarantine or Biosecurity Practices: Use suitable separate observation and dedicated tools. Any dip, rinse or egg intervention must match the host and exact formulation; refer hazardous tissue work, and keep quarantine or treatment water out of the display.

Equipment Inspection: Check pumps, air supply, surface agitation, skimmer, filter socks, carbon reactor, heaters, quarantine equipment, GFCI outlets, and emergency water-change equipment before treatment and during recovery.

Early Warning Signs: One rust-colored gliding animal, repeated worms on a coral base, new oval bite marks, reduced Acropora polyp extension, small egg clusters on bare skeleton, or a growing patch on lit rock or glass.

Recurrence Prevention: Continue non-invasive inspection after adults disappear, document egg sites, prevent transfer and reassess the identified host-specific plan. Do not improvise egg scraping or cut encrusted bases, and do not assume one product or fixed interval establishes clearance.

Common Mistakes

Mistake 1: Treating all reef flatworms as the same pest and using one control plan for red acoels and coral-eating species.

Why It Matters: Using one treatment for unrelated flatworms can leave coral-eating adults or eggs in place, expose sensitive livestock unnecessarily, and delay the host-specific control that damaged coral needs.

What to Do Instead: Identify the group, host association and fresh feeding damage. Controlled collection of accessible free-living nuisance acoels differs from a coral-host adult-and-egg plan. Refer hazardous or invasive host work; do not transfer a whole-tank product or assume universal egg removal.

Mistake 2: Killing a dense flatworm population at once without preparing carbon, aeration, filtration, and saltwater.

Why It Matters: A rapid die-off can release substantial organic material and defensive compounds, reduce dissolved oxygen, raise ammonia, and stress fish, coral, and invertebrates before enough waste is exported.

What to Do Instead: Siphon the population down in stages, confirm whether coral hosts and eggs need separate treatment, and prepare fresh carbon, matched saltwater, mechanical filtration, aeration, and monitoring before using a labeled product.

Related

Related Common Problems: Coral tissue loss; coral polyp retraction; coral bleaching; red bugs; nudibranch pests; live-rock hitchhikers; cloudy water; ammonia spikes; low dissolved oxygen; pest outbreaks.

Related Water-Quality Guides: Ammonia; Nitrite; Nitrate; Phosphate; Salinity; Temperature; pH; Alkalinity; Dissolved Oxygen; Copper; Water Changes.

Related Equipment Guides: Protein Skimmers; Activated Carbon; Carbon Reactors; Filter Socks; Sumps; Air Pumps; Powerheads; Quarantine Tanks; Siphons; Water-Test Equipment.

Related Maintenance or Setup Guides: Coral Quarantine; Coral Dipping; Frag-Plug Inspection; Pest Inspection; Water Changes; Mechanical Filtration; Activated Carbon Use; Equipment Sanitizing; Responsible Marine Livestock Disposal.

Related Livestock, Plant, or Coral Guides: Acropora Corals; SPS Corals; Wrasses; Blue Velvet Nudibranch; Copepods; Amphipods; Coral-Eating Nudibranchs; Red Bugs; Reef Invertebrates.

Sources & Evidence

Authoritative Source 1: Rawlinson and Stella, PLOS ONE (2012) - Discovery of the Corallivorous Polyclad Flatworm, Amakusaplana acroporae, on the Great Barrier Reef, Australia — the First Report from the Wild: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0042240. Scope: Corallivorous polyclad, Acropora host association, camouflage and egg batches. Limitation: Historical article title retained; accepted guide name is Prosthiostomum acroporae. Not a universal dip/egg interval, product test or every red acoel's biology.

Authoritative Source 2: World Register of Marine Species - Prosthiostomum acroporae accepted taxon record: https://www.marinespecies.org/rest/AphiaRecordByAphiaID/1353868. Scope: Accepted Prosthiostomum acroporae, Polycladida and Prosthiostomidae. Limitation: Taxonomy only; no control protocol.

Authoritative Source 3: World Register of Marine Species - Convolutriloba accepted taxon record: https://www.marinespecies.org/rest/AphiaRecordsByName/Convolutriloba?like=false&marine_only=true. Scope: Accepted marine Convolutriloba in Acoela, not a freshwater planarian or Acropora-feeding polyclad. Limitation: Not identification of every rust-colored specimen or product efficacy.

Additional Sources: Salifert - Flatworm eXit: https://www.salifert.com/rem/fe.htm. No dose, escalation, carbon amount, water-change percentage or treatment-time recipe reproduced; no AEFW, egg-kill or universal reef-safe extrapolation. Than Thein, Tidal Gardens - Pests: https://tidalgardens.com/articles/coral-care-articles/pests.html. Scoped aquarium observations, not universal experiments. Aggressive-dose dips, pesticide/dewormer suggestions, zoanthid scraping and paper-towel methods are explicitly excluded. Merck Veterinary Manual - Environmental Diseases of Aquatic Animals in Aquatic Systems: https://www.merckvetmanual.com/exotic-and-laboratory-animals/aquatic-systems/environmental-diseases-of-aquatic-animals-in-aquatic-systems. Not pest eradication, fixed water-change percentages or blind pH correction; pH/temperature influence ammonia toxicity and abrupt correction of acidic high-TAN water can worsen exposure. Hamade et al., CDC MMWR - Suspected Palytoxin Inhalation Exposures Associated with Zoanthid Corals in Aquarium Shops and Homes — Alaska, 2012–2014: https://www.cdc.gov/mmwr/preview/mmwrhtml/mm6431a4.htm. Associative reports; no safe DIY cutting, scraping, heat, bleach/decontamination recipe or invented clinical care is provided. Requests capture returned 403; web_fetch discussion was successfully read. National Capital Poison Center - Contact us: https://www.poison.org/contact-us. Not a worm-specific extraction or first-aid protocol; no tape, tweezers, rubbing, cutting or digging prescription is inferred.

Areas Where Reliable Sources Disagree: Evidence limits differ by identified organism, host and method. Biological or taxonomy sources do not establish treatment efficacy; manufacturer documents cover only the exact product. No universal predator compatibility, clearance interval or safe-return date is inferred. Unsupported precise control prescriptions are narrowed or removed rather than presented as consensus.

Claims That Require Owner Review: Under the owner's 2026-10-07 recovery authorization, unsupported precision and hazardous DIY methods are qualified or removed in this worksheet. No new dose, off-label drug, safe-predator guarantee or consumer hazardous-coral procedure is proposed. Source-recovery readiness does not itself authorize normalization or publication.

Problem-Specific Information

Anything Important That Does Not Fit Above: “Flatworm” is a visual description shared by several groups, and “red planaria” is often taxonomically inaccurate. The guide should use the hobby term for searchability while explaining that identification must be based on body form, behavior, host, feeding damage, and eggs.

Fields That Were Not Applicable and Why: Freshwater, planted-aquarium, and pond fields are marked not applicable because this guide concerns marine reef flatworms. Medication fields remain applicable because whole-tank products and coral dips carry important livestock and die-off risks.