cleaning off live rock


New member
I had an unexpected and extended absence from home and I returned to a tank completely overrun with algae - thick slime algae growing on every surface and killed all my sps. I have a few softies left. I've tried to manually remove as much as I can, but at this point I think the only feasible thing is to just start over.

My question is - how can I clean off the live rock? Can I simply wash it off with fresh water or will that kill all the good stuff on the rocks?

I plan to break the tank down and clean everything off. Then let the tank stabilize before introducing new corals.

Thank you!


Cloning Around
Staff member
RC Mod
Premium Member
Depends upon what you mean by "good stuff on the rocks." If you want to preserve stuff above the bacterial level, I'd personally scrub each rock with a stiff brush in a bucket of old saltwater, then put it in a tank (or just an old tub) of saltwater with circulation, no lighting, and a phosphate remover (rowaphos or chemipure) for several weeks before setting up in a tank with fresh saltwater and lighting.

If you only mean keeping the bacteria, then rinsing/scrubbing in freshwater would be fine - you'll kill some of the bacteria, but enough will be left to repopulate once you put the rock back in the tank. Depending upon how long the FW rinse is, some smaller inverts deep in the rock (small snails and worms) may well survive.

If you really only want rock that you can bacterially repopulate once it's clean, then a good soak in a mild muriatic acid solution will kill everything, followed by a thorough FW rinsing is good, or some people put their rocks into a bleach solution, then let them sit in the sun (ie, completely dry out) before rinsing and putting back into a tank.

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New member
Super helpful!. I was hoping to keep bacteria and just kind of blast off the slime algae. Sounds like it would be ok to just blast it with FW to knock the algae off. Maybe I'll do it in stages and scrub it in old SW like you suggested to try to preserve whatever is there. Great advice. Thank you Kevin!!!