Aquarium · Reef care
Coral fragging & propagation timing calculator
Fragging, cutting a piece off a coral colony to grow as a new piece, is how reef keepers propagate their own stock and trade with other hobbyists. The cut itself is the easy part. Knowing when a frag has actually recovered enough to handle, move, or sell, and when the parent colony is ready to be cut again, is where most of the real judgment calls happen. This calculator gives you a realistic healing window by coral type, plus a check against cutting a colony too soon after you've acquired it.
Estimated healing window
7–21 days
Judge healing by the frag itself, not the calendar: full polyp extension, no tissue recession, and visible new growth or encrustation at the cut are the real signs it's recovered.
What to actually buy
Blue Ocean Corals Coral Rx Dip
Dipping the parent colony before fragging reduces the risk of introducing pests or infection right when the coral already has an open wound to manage. This is a standard pre-cut step in most fragging guides, done on the colony itself, not the fresh cut.
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How this is calculated
Healing speed varies enormously by coral type, which is why this isn't a single number. Soft corals (leathers, polyps, xenia) are the fastest and most forgiving, typically closing over and reattaching within about a week, sometimes stretching to two or three depending on the cut and how well it's anchored. Mushrooms and zoanthids take slightly longer, 1 to 2 weeks, to form a new mouth and fully open back up.
LPS corals like hammer, torch, and frogspawn heal more slowly, the cut surface itself closes over in 1 to 3 weeks, but full tentacle re-extension can take 2 to 4 weeks or more depending on species. SPS corals (Acropora, Montipora) are the slowest: full encrustation over the cut base takes a month or more. These ranges come from AllCorals' and Reefbay's fragging guides, both widely used references in the reefing hobby.
The acquisition check is separate from healing time. Hobbyist consensus, reflected in both source guides, is to let a newly acquired colony settle into your tank and show strong, consistent growth for 4 to 6 months before cutting it for the first time. A coral that's still acclimating to new water parameters and lighting doesn't have the energy reserves to recover from a cut as reliably as an established one.
Sources
Frequently asked questions
Can I speed up frag healing?
Stable water parameters, good flow across the cut surface, and keeping the frag somewhere it won't get knocked around matter more than anything else. Dipping the parent colony before cutting (not the open wound itself) reduces infection risk, which indirectly protects healing speed, but there's no real shortcut to the biological process itself.
My frag looks fully healed well before the estimated window, can I move it?
Trust visible signs over the calendar: full polyp extension, no tissue recession, and visible new growth or encrustation at the cut all indicate real recovery. Soft corals and mushrooms in particular can genuinely heal faster than the estimate in good conditions.
Does frag size affect healing time?
Yes, generally, a larger frag with more surviving tissue and energy reserves heals a cut faster relative to its size than a tiny sliver with very little tissue to work with. This calculator's ranges assume a reasonably sized, healthy frag, not an unusually small or stressed fragment.
What's actually risky about cutting a colony too soon after acquiring it?
A coral that hasn't finished acclimating to new lighting, flow, and water chemistry is already under some stress, and fragging adds a real wound on top of that. The combined stress can set back the whole colony's health, not just the piece you cut off, which is the reason behind the 4-6 month settling-in window.