A frag plug is a small ceramic or aragonite disc (typically 1-1.5 inch diameter) used to mount coral fragments. The plug is glued or pressed into rockwork after the coral has encrusted onto it.
Practical use in aquariums
Buy plugs unaccompanied or pre-bonded with cyanoacrylate (CA) gel + reef putty. Soak new plugs in RODI water for 24 hours before use to leach any residue. Mount the frag with reef putty + a drop of CA gel - the putty holds shape, the CA flash-bonds the coral to the plug.
How Frag Plug fits the bigger picture
Understanding Frag Plug matters because it's connected to broader husbandry decisions: fragging skill compounds: the more you frag, the more you understand coral biology + propagate your own pieces.
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.
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.