Rainbow Mille Acropora Propagation Guide
Propagation of the 'Rainbow' color morph of Acropora millepora, a multicolored small-polyp stony coral propagated by branch-tip fragging under high light and low nutrients.
Overview
"Rainbow" is a multicolored color morph of Acropora millepora, a small-polyp stony coral in the family Acroporidae. Wikipedia describes A. millepora as a small colonial coral growing in clumps of short cylindrical branches with uniform, scale-like radial corallites bearing projecting lower rims. The wild colour is naturally variable — green with orange-tipped branches, pale pink, orange, plain green or blue — and the Rainbow morph is a selection combining green, blue, pink and purple tones across the branches.
Reproductive Mode
Acropora reproduce asexually and sexually; in aquaria the Rainbow morph is increased by fragmentation. As a zooxanthellate coral it hosts symbiotic dinoflagellates (Symbiodinium) that photosynthesise to feed it, so fragments retain the parent's symbionts and coloration. Wikipedia notes captive propagation of Acropora is widespread among reef keepers.
Fragging / Asexual Propagation
Cut or snap a branch tip of about 2-5 cm with bone-cutters and fix it to a frag plug with cyanoacrylate gel or epoxy. The axial corallite at the branch tip leads regrowth, so an intact tip encrusts and extends faster. Wikipedia reports finger-sized fragments can become medicine-ball-sized colonies in one to two years under good conditions.
Conditions for Propagation
Wikipedia states Acropora requires bright light, stable temperatures, regular calcium and alkalinity dosing, and clean turbulent water. The Rainbow morph shows its multiple colours most strongly with low nutrients, so place frags under high light and strong flow with stable alkalinity, calcium and magnesium and tightly controlled nutrients.
Sexual Reproduction
In the wild Acropora reproduce by annual synchronised broadcast mass-spawning, releasing buoyant egg-and-sperm packets into the water column for external fertilisation. Home aquaria do not normally reproduce this, relying on fragmentation instead.