Ulcers and body wounds in discus: causes, treatment, tissue regeneration

In short

• Ulcers = open lesions with craters on the body, often with inflamed red edges.
• Wounds = mechanical trauma (nipping, decor) — fast healing if you treat them.
• Main causes: mechanical trauma (decor, nipping), bacterial infection (Aeromonas), Columnaris, Mycobacterium.
• Key differentiator: a single isolated one = trauma. Multiple, asymmetric, won't heal = infection or Mycobacterium.
• Treatment: eSHa 2000 + Epsom salt 1 g/L + catappa leaves + impeccably clean water.
• Do NOT use creams or "human" topical antiseptics — toxic to fish.
• Permanent scars possible after large ulcers (cosmetic, no functional impact).

What you'll learn from this guide

Ulcers and body wounds in discus (Symphysodon) are among the most common and alarming visual problems — the fish's skin is its most exposed organ, and its deterioration almost always signals something wrong. A simple wound (from hitting decor) heals in 1-2 weeks with clean water, but a recurrent ulcer or multiple asymmetric ulcers can be a sign of an internal bacterial infection (Aeromonas hydrophila), Columnaris or even Mycobacterium (zoonotic!). This guide shows you how to tell a trivial wound from a serious infection, how to apply the treatment protocol with eSHa 2000 + Epsom salt + catappa leaves, and how to stimulate tissue regeneration for optimal scarring.

What ulcers and wounds are — quick anatomy

Key idea: any wound in discus can become an ulcer if the water isn't clean or the protective slime coat is compromised.

The 6 main causes — differentiation

Cause 1 — Mechanical trauma (40% of cases)

The most common and easiest to treat.

Characteristic signs:

• ✅ A single isolated one in one area
• ✅ Normal fish behavior (eats, swims)
• ✅ Possible fresh blood at appearance
• ✅ Sudden appearance (overnight)
• ✅ Location consistent with the decor (side near a rock, under the pectoral fin from scraping the bottom)

Sources:

• Unprocessed wood with sharp edges
• Pointed stones
• Scraping on filters/cables
• Nipping between discus (sides or fins)
• Handling with a net

Cause 2 — Bacterial infection (Aeromonas) (25%)

Opportunistic bacteria attack existing wounds.

Characteristic signs:

• ❌ The wound does NOT heal after 7 days with clean water
• ❌ Inflamed red edges that spread
• ❌ A progressively deepening crater
• ❌ White/yellow slime on the surface
• ❌ Possible intermittent bleeding
• ❌ The fish becomes slightly lethargic

Cause 3 — Columnaris (15%)

An aggressive filamentous bacterium (Flavobacterium columnare).

Characteristic signs:

• ❌ FLAT yellowish-white patches that spread fast
• ❌ Common location: mouth, head, base of the fins
• ❌ 24-72h spread
• ❌ Red bleeding ulcer edges
• ❌ The fish becomes lethargic quickly

Cause 4 — Saprolegnia on old wounds (10%)

Fungus on already-dead tissue.

Characteristic signs:

• ✅ FLUFFY white filaments like cotton wool
• ✅ 3D — moves in the current
• ✅ On old wounds that haven't healed
• ✅ Edges without inflammation
• ✅ Slow spread (days-weeks)

Cause 5 — Mycobacterium (5-10%) ⚠️ ZOONOTIC

A chronic incurable disease — a real human risk.

Characteristic signs:

• ❌ Multiple asymmetric ulcers that do NOT heal
• ❌ Chronic weight loss (months)
• ❌ Possible spinal deformity (S-shape)
• ❌ Classic antibiotic treatments do NOT work
• ❌ Several fish affected one after another (months)

⚠️ NITRILE GLOVES MANDATORY — see Mycobacterium guide.

Cause 6 — Advanced Hexamita → HITH with erosions (5%)

See Hexamita / HITH.

• ❌ Erosions on the head and lateral line
• ❌ Combined with stringy white feces
• ❌ Visible weight loss with a sunken belly

Quick differentiation table

🎯 Quick diagnostic test: A single wound + the fish eats + sudden appearance = 95% trauma. Multiple asymmetric ulcers + chronic weight loss + no treatment response = a serious suspect.

Treatment — step by step

Step 1 — Identify and remove the CAUSE

Before any treatment, ask yourself WHY:

Step 2 — Impeccable water (THE FOUNDATION)

Without clean water, no treatment works durably.

Step 3 — Epsom salt (reduces inflammation + stimulates healing)

A dual mechanism:

• Reduces inflammation of the ulcerated tissue
• Stimulates the evacuation of toxic residue from the lesion area
• Helps recover osmoregulation

Step 4 — Antibiotic (for wounds that won't heal)

Option A: eSHa 2000 ⭐ TOP RECOMMENDATION

Procedure:

1. Remove the activated carbon (CRITICAL)
2. Maximum aeration
3. Initial dose 5 ml/50L
4. 25% change / day with proportional re-dosing (days 2-5)
5. Day 6: 50% change + new activated carbon

Option B: Waterlife Myxazin (specific to Columnaris + ulcers)

• Online EU, approx. €19–25 (RO estimate)
• Per the manufacturer
• Excellent for ulcers with red edges

Option C: Sera Baktopur Direct (severe cases)

• Nifurpirinol, 1 tablet / 20L (5.3 US gal)
• 2 days + repeat
• approx. €11–15 (RO estimate)

Option D: Kanamycin (deep internal + external)

• Requires a veterinary prescription
• 250 mg / 40L (11 US gal)
• 5-7 days + medicated food
• For very severe ulcers with suspected septicemia

🧮 For the exact dose on the net volume (minus substrate / decor), use the treatment calculator.

Step 5 — Catappa leaves (natural regeneration)

Indian almond leaves (Terminalia catappa) release tannins that:

• A natural antibacterial
• A mild antifungal
• Speed up scarring
• Calm stress

Step 6 — Tissue regeneration support

Estimated healing time

Scars are cosmetic — the fish remains functionally healthy. In fact, a scar indicates complete healing — preferable to a chronically open wound.

Severe cases — an intensive protocol

For large ulcers (>1 cm / 0.4 in) or with suspected septicemia:

Intensive hospital tank

1. Set up a hospital tank 80L+ (21 US gal+) with a mature sponge filter
2. Water 50% from the main tank + 50% fresh dechlorinated
3. Stable temperature 29°C (84°F) (do NOT raise it!)
4. Maximum aeration 2 pumps + diffuser

Combined treatment

Medicated feeding (additional)

For ulcers that don't respond to the antibiotic bath:

Feed 2× / day, 7 consecutive days. Kanamycin reaches internally through the digestive tract → attacks systemic bacteria.

Common mistakes

❌ Creams/antiseptics from the human pharmacy (Betadine, etc.) topically on the wound → toxic to fish, extreme stress, worsening.

❌ Treating ONLY the ulcer, not the cause → recurrence in 1-2 weeks. The primary cause (decor, aggressor, water) must be removed.

❌ An antibiotic before checking the water → 50% of wounds heal with impeccably clean water ALONE.

❌ Activated carbon in the filter during treatment → it absorbs the medication, zero treatment.

❌ Large changes (>50%) in the middle of treatment → you dilute the medication abruptly.

❌ Combining eSHa 2000 + Methylene Blue + Epsom salt + catappa leaves ALL at once → some combinations are safe (Epsom salt + eSHa 2000 + catappa), others are NOT (eSHa 2000 + Methylene Blue at high doses).

❌ Keeping sharp decor → new wounds continuously, a vicious cycle.

❌ Reintroduction to the main tank before complete healing → secondary infection.

❌ Frequent handling with a net → loss of the protective slime coat, the ulcer drags on.

❌ NOT checking other fish → an ignored systemic disease, mass loss.

Prevention — how to avoid ulcers

See also Decor / hardscape and How to choose a healthy discus.

When to consult a specialist

• Multiple asymmetric ulcers + chronic weight loss → suspect Mycobacterium
• A complete 2-week treatment with no result
• Several fish affected at once → a systemic cause
• An ulcer deepening to the internal organs (visible structure)
• Suspected septicemia (generalized red skin)
• Recurrence after apparent healing

Post on dedicated forums with macro photos (from different angles) + water parameters + recent history (purchases, changes, other symptoms) — or contact breeders from the Discus.ro directory.

Final checklist — managing ulcers

Diagnosis

• ☐ Identified the type (trauma / infection / Columnaris / Mycobacterium)
• ☐ Differentiated with the comparison table
• ☐ Checked other symptoms (weight loss? several fish?)
• ☐ Inspected the decor and the hierarchy

Treatment

• ☐ Removed the primary cause (decor / aggressor / water)
• ☐ 30% changes / day with Prime
• ☐ Epsom salt 1 g/L
• ☐ Catappa leaves
• ☐ If it doesn't heal in 7 days → eSHa 2000
• ☐ Removed the activated carbon
• ☐ Maximum aeration
• ☐ Temperature 29°C (84°F) stable

Support

• ☐ A vitamin supplement in food 2× / day
• ☐ A high-protein diet
• ☐ Garlic 2× / week
• ☐ Reduced lights 2 weeks
• ☐ Reduced current 2 weeks

Monitoring

• ☐ Daily photo for progression
• ☐ Checked other affected fish
• ☐ Water test daily
• ☐ Documented the scar (cosmetic, not functional)

What to do next

📚 Continue learning:

• Columnaris in discus — on the mouth + head, aggressive
• Saprolegnia (fungus) — on old wounds
• Mycobacterium / fish TB — chronic ulcers
• Fin Rot in discus — fin erosions
• The essential aquarist's pharmacy — the complete kit

🔧 Practical resources:

• Treatment dosage calculator — eSHa 2000, Epsom salt
• Visual diagnosis — at the first signs
• Aquarium treatments — shop
• Decor / hardscape — soft wood, rounded stones

🐠 Final tip: Ulcers are the alarm that something is wrong — environment, hierarchy, or a systemic disease. Clean water + Epsom salt + catappa leaves = 70% of wounds heal without an antibiotic. The antibiotic comes in only if it doesn't heal in 7 days. ALWAYS investigate the cause — an aquarium with recurrent ulcers has a fundamental problem (dangerous decor, a chronic aggressor, bad water, or a disease in the tank). With correct management, a healthy discus's skin stays flawless for life.