Someone recently posted a question about using some cured live rock from his friend’s tank. The short answer is of course you can, but there are definitely a few things to keep in mind when picking up some live rock that may have been around for a while. Here’s a list of things that I would suggest looking out for when picking up live rock both in and out of your local fish shop.

But first, I’ve gotten a lot of questions about the terms curing or cured when referring to live rock. The term cured, means that the rock has been allowed sufficient time to let organisms on it die away. When they harvest this rock, whether it is manmade or natural, it grows in the ocean, and there may be a great many things living on any given rock, from shrimp to sponges to corals and plenty more. Unfortunately, by the time this rock makes it into your local fish store, many of these things have died, or are in the process of dying. The rock must then be cured, meaning that when fully cured, there will be no more organisms dying off, and it may now safely be put into a tank. When I check out fresh live rock in a store, I usually give it a smell test. I’ll look on the rock first, for any obvious red flags, but a whiff of the rock may reveal things you may not notice at first. Foul smells usually mean that something is still dying off, and that rock is probably not a good choice. If it smells like the ocean, its good.

But just because a rock is cured doesn’t always mean that it’s ok for your new reef tank. Futballer asked about getting cured rock from his friend’s old tank. If his friend’s aquarium is a thriving reef tank, then yes, it would probably be an excellent place to get live rock from, but I would be sure to keep these in mind when checking out any new live rock for yourself.

Pests or nuisance algae

Common thing people may introduce to their tanks when not cautious include Aiptasia or glass anemone, flatworms, bristle worms, hair algae, bubble algae, and cyanobacteria or red slime algae (may be green too). Basically, you want to keep from infesting your tank with something that may be a problem later. All of the nuisances listed above can be solved relatively easily, but this usually happens before the rock is introduced to the tank to avoid bigger issues.

Is it still alive?

Occasionally, I’ll come across saltwater tanks that haven’t been run for a long time, with live rock and equipment still in place, but no fish. Usually, there isn’t a mass of dying corals on top, in which case I would probably re-cure the rocks for a while. But when the rocks are clean, I look at two things: How long since fish were last in the tank, and whether or not the tank was ever medicated. Usually, a reef tank’s live rock would find a good home fairly quickly, so if the tank has been sitting for a while it was most likely just a fish-only type tank.

If the tank was ever medicated with copper, I would not recommend adding that rock to your reef tank. It would likely harm invertebrates and corals you’ll want to add. But if the tank was never medicated I will ask how long since the last fish were in there to get a sense of how “live” rock is, with regards to beneficial bacteria. If the rock has been sitting for months with no fish, then not only has there been no food to keep the bacteria thriving, but the salinity is probably pretty off too. A more recent fish load may suggest that the rocks are still plenty “live” and good for a new tank. But in either case, the rock may be used, though older rock may be less beneficial if you need bacteria immediately for cycling purposes.

Someone breaking down a tank or a friend with an established tank can be an awesome way to get nice live rock for far less than fish shop prices. But knowing what to look out for can save you plenty of headaches, and may even be that thing that saves you from wanting out of the hobby. Hope this helps you on the road ahead Futballer.

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