Hyposalinity exploits osmoregulation differences between fish and parasites. Protocol: 1) Move fish to bare-bottom QT with sponge filter. 2) Drop salinity from 35 ppt to 16 ppt over 24 hours. 3) Continue dropping to 12 ppt over the next 24-48h (1.009 SG). 4) Hold at 12 ppt for 14-21 days. 5) Slowly raise back to 35 ppt over 2-3 weeks before transferring to display. Why it works: Cryptocaryon irritans (marine ich) cannot survive below 16 ppt - osmotic pressure ruptures cells. Most marine teleost fish tolerate 12 ppt because they actively regulate internal salt balance. What it kills: ich, velvet (some strains), brooklynella. What it does NOT kill: some bacterial infections, flukes (still need prazi), certain parasites. Risks: stresses fish, can damage scaleless species (eels, sharks), kills any inverts present, kills coral. Use ONLY in dedicated QT - never in display. Alternatives: copper at 2.0 ppm Cu (effective + safer for fish but kills inverts), tank transfer method (TTM, no medication), formalin baths.
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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.
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.
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