SALTWATER disease

Tang Spot Syndrome (Lateral-line disease in tangs)

Reviewed by the Fast Aquatics husbandry team · Updated May 2026

Quick referenceTang Spot Syndrome (TSS) is a head + lateral line erosion specific to tangs + surgeonfish. Linked to stress, low-quality diet, vitamin deficiency, and chronic high nitrate. Reverse with diet + water quality.

Symptoms

Pits along lateral line
Sunken patches on head
Color fade
Refusing food
Sluggish swimming
Worsens with stress

Cause

Multifactorial: 1) Spironucleus protozoa parasites. 2) Vitamin C + A deficiency (poor diet). 3) Chronic high nitrate (>30 ppm). 4) Stress from confinement, aggressive tankmates, undersized tank.

Treatment options

Diet upgrade. Soaked nori + Selcon + Vita-Chem 3x weekly. Add fresh garlic supplement. Switch to NLS Marine Pellet or Hikari Marine Pellet.
Metronidazole. Targets Spironucleus. Soak pellets in metro for 30 min, feed for 7-10 days.
Reduce nitrate. Larger water changes, refugium with chaeto, biopellets if reef tank.
Stop GAC (debated). Some studies link granular activated carbon to HLLE in tangs. Try ceasing GAC for 6-8 weeks.

Always treat in a separate quarantine or hospital tank.

Prevention

Provide adequate tank size (75g+ for yellow tang, 125g+ for hippo, 180g+ for Naso/Vlamingii). Vary diet daily. Maintain nitrate <10 ppm. Reduce stress.

Fatality + outcome

Slow but progressive. Untreated severe TSS causes permanent disfigurement; mild cases reverse fully with treatment.

Full disease database · Symptom matcher · Q&A library · QT calculator

Aquarium-keeping fundamentals

Whatever specific topic brought you here, four fundamentals govern long-term aquarium success: water quality, parameter stability, biological filtration, and species-appropriate husbandry. Skip any one and the others struggle to compensate.

Water quality: ammonia + nitrite at zero, nitrate under 30 ppm freshwater + 10 ppm reef. Test weekly with API or Salifert kits. Use our water parameter checker to score your readings against your tank type.

Parameter stability: stable wrong parameters beat fluctuating ideal parameters. Most fish tolerate a wide pH range if it's stable. Sudden swings of 0.4+ pH or 5+°F kill fish faster than chronic suboptimal values. Use temperature controllers (Inkbird) + automated dosing for consistency.

Biological filtration: the bacterial colony on your filter media + rock + substrate is the engine. Never replace all media at once. Use our filter turnover calculator to size correctly.

Species-appropriate husbandry: research adult size, territoriality, diet, and tankmate compatibility before purchase. Use our tank stocking calculator + compatibility guides.

Frequently asked questions

How long does an aquarium take to set up? 4-6 weeks for full cycling + first stocking. Use our cycle ETA calculator + how long does cycling take.

What's the best aquarium for beginners? 20-gallon long. Big enough for parameter stability, small enough for budget + space. See beginner picks.

How often should I do water changes? 25-30% weekly. See water change frequency Q&A + water change calculator.

Why does my fish keep dying? 5 leading causes: uncycled tank, wrong species pairings, no quarantine, undersized tank, neglected water-change schedule. See full diagnosis.