Need help with used live rock condition

[Wet Fish]

Need some help new to this saltwater stuff .
Should the live rock have dark green to black Algae on it??? (has some good pink algeas too) I also have large shells that have dark green & black algae? Is that OK to put back into the tank once I remove sand and replace with new water. (new water is RO water that I will be adding proper salt mix) Also some of the smaller piece really stink of dead fish.
I’m in the process of tearing down a used tank I bought and removing the sand all the stinky dead stuff it contains.
As I taking apart I’m still finding live crabs which I’m relocating to a better environment until I wash the tank and fill with fresh salt water.
The plan was to remove all the sand and just put the live rock back in for now, but I’m afraid I will be putting bad rock back in???

[Gti_Leo]

is the rock still wet or is it all dried out? if its dried out the algae is probably all dead, so you can just begin a new cycle once you put it in salt water, if its still wet then put it in buckets and every day scrub it with a stiff brissel nail brush untill all the crap algae is off. be sure to do this in a separate bucket though, as you don't want the algae to reattach to the rock

i'd also suspect there to be some unwanted hitchhickers so a good way to remove them is to put the rock in water with a SG of 1.040 and they critters will quickly evacuate and you can remove them

[mr_X]

if that rock stinks like dead fish, it will need to be re-cured. i wouldn't worry too much about the algae. it will die off during the cycle most likely. just don't add any livestock to the tank until you are sure the tank is cycled, and don't run the lights while the tank is cycling.

[Wet Fish]

All critters accounted for,,,,, gonna start scrubbing the rock and probably toss some of shells out. I goning to scrub it and let it dry out and decide what worth keeping...