Soaking old live rock in RO.

[sidney109]

Hello.

Im coming back into the hobby with all my old live rock ( now really dead as its been dry for years) i have been soaking it in ro water now for a week or 2 and replacing the water every few days, my question is when do you stop this process as im just using a TDS meter on the water to watch when its soaking stuff out the rocks, first day it went to 750ppm! after a few soaks its sitting at 120ppm now but i cant decide if its soaking anything bad out or just melting the rock somehow.

when would you stop with the RO and salt it up and cycle the rock out, it can stay in the tank its in for months if needed as it was my old quarantine tank in the shed.

thanks in advance for any help you could give

sid

 

[PatW]

There are 2 major issues with old live rock.

The first is dried organics on the rock which hydrate, add nutrients to the tank and possibly stink. Soaking in diluted bleach for a day or two will usually remove these. In your case, they are probably long gone.

The second are phosphates. Phosphates can get absorbed by rock and will leach out into the tank causing algae issues. One way to see if these are an issue is curing in saltwater for a week or more and testing with a Hanna ULR phosphorous detector. I would think most of these have leached out by now. If you are thinking of a low nutrient SPS system, you might take some of your RODI soaking water, add enough salt mix to get it up to bout 35 ppt and testing it either yourself or the LFS. But it is probably not necessary.