how long for dry base to mature?

[cracker]

hello, I have a 75 that's about 2 &1/2 yrs old .. There are several older large base pieces in there that are looking like an aquatic Chia pet rocks. I want to remove these rocks . one at a time of course & replace with dry base. Iv'e already swapped out one. What's your Op on how long to wait before the rock is "mature" enough to change another? These rocks are very old & I suspect loaded up with nutrients, feeding the HA. The rest of the rock is much better. This rock is very dense & I think I can get a better/ more porous rock. Thanks !

 

[Reefing Madness]

Its just like curing rock, best guess would be 4-6 weeks