Posted by @Chris_Lewis · 1h ago
Your rock is the biological heart of a reef tank, and how you start it shapes your first few months.
Live rock comes already colonized with bacteria, and often coralline algae and tiny inverts. It can cycle a tank fast — sometimes it is nearly ready out of the gate. The trade-offs: it costs more, and it can carry hitchhikers you did not order, from harmless copepods to aiptasia, pest crabs, or worse.
Dry rock is clean, dead rock. No pests, lower cost, and full control. The trade-off is you must cycle it from scratch (seed it with bottled bacteria or one piece of live rock), which takes the usual few weeks, and coralline has to grow in over time.
A popular middle path: mostly dry rock for the aquascape, plus one cured live rock piece to seed the bacteria. Most of the speed, far less pest risk.
Either way, cycle fully before adding anything. The process mirrors freshwater — ammonia to nitrite to nitrate — so the glossary entry on the nitrogen cycle applies here too.
Your turn: did you go live, dry, or mixed — and did any hitchhikers show up? Photos of mystery critters welcome; someone here can usually ID them.