When I remove rock, it goes in the garden. My line of thought is that rock in a closed system has a finite lifespan. To alleviate this somewhat, I regularly turkey baste the exposed rock to clear the pores.
At the 3 year mark of my tank, 90% of my rock has been replaced. NO3 and PO4 still 0. I have never had measurable amounts of either. Based on that, I'm going to stick to my ideas on old rock :)

Maybe I'm misunderstanding but I've always thought that live rock was an excellent source of a "natural flirtation". I've always kept lots of live rock in my sumps over the years. I won't use filter socks so there there is a build up of detritus in my sump. But all WCs are done in the sump and I vacuum it out with a shopvac every couple of months. I have about 75lbs in my sump right now.

Further, I do think you can "recycle" used rock to a degree by cooking, and maybe get a year or three more out of it. Buying new rock is tough, as most LFS that I know of don't have new rock, they have used rock that they buy from people shutting down. So unless you're ordering a fresh box, you may get worse rock than you took out.

Bill, yes, the rock is filtration, but the amount needed is usually far less than most people add. Between the rock in the display and any sand/substrate, you have more than enough bacteria to filter most tanks. Adding more to the sump isn't required. If you have 0 or near 0 nitrate, you probably don't need more filtration.
Also, the ability to filter nutrients is dependent on the porosity of the rock, and rock that sits in the sump tends to plug up quickly, and therefore becomes useless as a filter. Going one step further, it will eventually begin to leach nutrients back into the system.

Ok thanks for the explanation. I'm a picky bastard so I don't let a lot of detritus to build up:lol:

Funny, this how most of us start out in the hobby. And this old rock isn't cheap! :mrgreen:

Oh, I know. My first big tank, a 150g, had almost 250 pounds of rock. Essentially a sewer with corals. Brown corals :) always had nutrient problems. Once I moved away from the rock pile look and used minimal rock, my tank has never been better.

I got more rock cuz I just got a bunch more sps and ran out of spots to glue them to due to my lack of LR in my display. I tossed them In the sump because I ran out of time last night to rearrange my whole tank plus I put my new pieces in a low light area temp to adjust to my LEDs. The rocks look pretty clean. I guess I can take them out n put in new salt water and blast them hard with a power head a few days then test nitrate n phosphates again before putting it in permanent spots.

Isnt most live rock older than 3 years? How do you know how longs its been in the ocean for . I agree that live rock will build up with crud if you don't have the right fauna to keep it clean but I don't think it expires . If you where really worried about it you could bleach the old rock to dissolve the organics then cure it/ re seed it , but maybe that's just me an im too cheap to throw something away that cost me 4$ a lb .

I agree, most of us don't throw it away. And my rock is the old crud from the LFS:sad: here it costs more than $4lb.
The rock from the ocean is old but it is treated by Mother Nature and doesn't exist in a glass box in artificial salt water.
IMO