Replacing existing live rock with cured dry rock

[FruiTee]

So i want to completely re do my aqua scape on my 120gal that's been running for 3 years now and i know I'll probably kick myself for this

When I started my tank I basically did what I could and Covid gripped my wallet so it was did what I could afford back then

Now I have nice lump of money saved I want to redo my aquascape

Basically my idea is to buy dry rock smash it up build my scape and put it in a bin with salt water bacterial supplement flow and a heater to cure

Once cured swap out my existing rock pieces either slow or fast

I have a few established corals on the rocks but I don't mind fragging and starting over again

What would be a good way to go about this

*edit I also have a 1 inch sand bed

 

[Lost in the Sauce]

What's the bioload like in the tank?

Do you maintain the sandbed?

 

[FruiTee]

What's the bioload like in the tank?

Do you maintain the sandbed?

Pretty light I have 7 small fish I feed once daily my nutrients are pretty low 0.04 po4 and 2ppm nitrates I don't run GFO or Nitrate Reactors

I used to siphon the sand during weekly changes but I stopped half a year ago because I was worried I would starve my sand sifting conch's and star fish

 

[Lost in the Sauce]

Do you have enough spare room in your sump to remove your existing rock from the display, get your cycled new aquascape set up and have a large portion of your original rock in the sump?

Then you could remove a few pieces a week and not have to worry about it

 

[Fatrip]

I agree with Lost, if you have the room cure the rock in your tank sump and remove a section at a time. Playing with fate relying on the other method you described to grow enough bacteria to replace rock for rock.

 

[FruiTee]

Do you have enough spare room in your sump to remove your existing rock from the display, get your cycled new aquascape set up and have a large portion of your original rock in the sump?

Then you could remove a few pieces a week and not have to worry about it

I can probably save a few pieces in the sump I haven't thought about that, thanks man I think this is the way I'm gonna go forward

 

[homer1475]

I would definitely put as much of the old rock in the sump for a while(a few months or so while things stabilize), just to keep things stable. All new rock, even though cycled, will be like starting the tank over.

 

[Lost in the Sauce]

You should also remember that just because you are replacing the bacterial component you are not replacing the algae competition so you will very likely have a new round of uglies.

 

[Starganderfish]

I just did this yesterday in my 4 gal AIO tank.
I pulled all the old rock out, siphoned the newly exposed sand bed to extract some of the built-up crud and then placed new dry rock in its place. Popped all the corals off the old rock and glued them onto the new, then did about an 80% water change. I was lucky that I had no fish in the tank at the time, because it got stirred up a bit but it cleared up really quick. 24 hours later Ammonia is a barely detectable hint on the Sera test and Notrates and Phosphates are stable to previous levels on Hanna tests.
I'll be testing and dosing with Prime every day for a week to manage any buildup but I'm not expecting any issues. I was able to add a new fish to the tank within about 2 hours (plus acclimation). Snails were unaffected, corals bounced back super quick and the new inhabitant is settling in fine.

It's worth remembering that the rock is only part of the tank's bacterial load - the sand-bed, glass, water, filter pads and bio media, chaeto in the fuge and any other objects in the tank also have nitrifying bacteria in or on them. It's the DEnitrifying bacteria, deep in the rock, which is probably going to take the most time to re-establish, and water changes are able to cope with any Nitrate buildup till then.