Question about redoing 1 tank of a 2 tank shared sump system

[exnisstech]

I have a 180 gallon and 150 gallon display tanks both up and running for a few years now. They are both plumbed together into a 125 gallon sump in my basement and share a return pump. I am really not happy with the 150 layout. I have probably 150 lbs of live rock in the 180 gallon and also have rock in the sump. I would like to take the 150 offline and redo it. I can move livestock around temporarily so that's not a problem. I want to clean the rock and buy some new rock also. Also I would like to remove the deep sand bed and either go bare bottom or shallow sand bed, still undecided. I'm wonder what your thoughts are about cycling after I get it all setup. Since I have so much rock in the sump and 180 that wont be disturbed do you think there would be much of a cycle in the 150 or is there a chance it would be instant? The 180 that will remain running has a deep sand bed also so I'm think maybe it would just be like doing a really large water change? I just don't want to kill everything so I'm seeking input from those of you with more knowledge than myself.

 

[JCM]

I'd redo it and just leave it offline until the water tests ok. You'll probably see some instability for a few days, when that goes away, put it back online.

 

[WVNed]

That is a complex question and has a complex answer based on info you didnt give.
What kind of new rock?
New rock and new sand or even a portion of the old sand that has been rinsed

Drain the tank, keep the old rock in the drained water and clean it.
Clean it of what and how?
Minimal time out of the water? Some basic scrubbing with no peroxides or bleach.

Put it all back together with new water and turn it on.

Rock hours out of water you are gluing together after soaking it in something.
It will cycle a bit. Let it happen and then turn it on.

 

[exnisstech]

Will be using live rock purchased from lfs that is several years old stored in bins with circulation. I'll also be using some of the current rock that will be stored in saltwater removed from the tank. There are just a few pieces that have some palys on it that I want to remove. I thought about new sand but could clean some of the sand in removed tank water so it would still be "live" sand if that would be better than new. I'm hopeing to be able to scape it without having to glue the rock together as that hasn't gone well for me in the past. The rock will be out of water for as long as it takes to cut the bottoms flat on the first layer and get everything scaped so there will be some die off. I suppose it may be safest to run it stand alone with powerheads for circulation and just test as I would a new set up till I'm sure it is cycled? Thinking out loud a bit.

 

[WVNed]

If you keep the rocks wet while you clean them and cut them they would be fine. Work on one and put it back and do another for a while.

You way is safe but I don't think you will see anything happen as far as a cycle.

 

[exnisstech]

I just figured I would update this for anyone else looking to maybe do something like this. It all went well. I completely drained the tank. All rock went into totes and remained covered with tank water. A couple of pieces were soaked in hot fresh water in hopes of removing a couple stray palys and a majano. I haven't seen them so maybe it worked. It sure did a number on a bunch of pods and asterina stars. I also removed all of the old sand. I scraped the entire tank clean which was great fun on a 29" deep tank on a 32" stand. I then put egg crate down and did the aquascape without having to actually cut any rock. I chiseled a few pieces to get a better fit and make it more stable. I then added 100 lbs of Arag Alive fiji pink sand. I'm really happy with the results as the tank was kind of hohum and cluttered before . Now it is so open I'm probably going to add more fish and limit the coral I keep to sand dwellers and maybe look for a nice clam as a centerpiece. All of my LPS and softies were moved into my 180 and I think it will stay there. Momma really likes it all on the end off the tank where I placed it as we walk past it anytime we go into any other room. The entire process was completed and up and running with fish back in in less than 36 hrs although I did work till 4 am the first night. I hate stopping in the middle of something. Momma tried to get me to stop and watch a movie with her. She's a funny Gal lol. Thank for the input provided that gave me the confidence to undertake this project. Now to wait for the coraline to cover the back wall. I had a Rocky 3D background on it left over from when it was freshwater. I should have painted it but didn't feel like disconnecting the plumbing and moving the tank. Yes there is a trim piece missing that I forgot to put back up before taking pics