disease

RTN

Rapid Tissue Necrosis

Definition

RTN (Rapid Tissue Necrosis) is a coral disease where tissue sloughs off the skeleton over hours to days, typically affecting SPS coral. Often triggered by parameter swings (alk swing >1 dKH/24h), AEFW infestation, low DO, or bacterial infection.

Practical use in aquariums

Treatment: cut healthy tissue away from the necrotic edge with sharp shears, frag onto a clean plug, dip the salvaged frag, mount in moderate flow. Stabilize tank parameters first - new pieces will RTN again if the underlying cause is not addressed. Test alk swing with daily measurements for 7 days.

How RTN fits the bigger picture

Understanding RTN matters because it's connected to broader husbandry decisions: disease prevention is cheaper than treatment - quarantine + dipping protocols paid back the first time you avoid a tank-wide outbreak.

Browse the Fast Aquatics care library for full husbandry tutorials covering RTN in context.

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.

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.