Is this a bad idea?
 

So the new 180 is almost full, I hope to add salt tonight, and the rock I've had in a tub for a month will go in over the weekend.
So here's the dilema. Lots of the gear I need is on the 90. So my thought is to shut down sump, move over skimmer/reactor/zeo setup and maybe remove the 2 Tunzes from the 90 and replace with smaller pumps.
Now this will be for about 2 weeks, until I'm happy with the 180 and can start moving stuff over. Only 2 pieces of rock from the 90 will go, so 180 is mostly new with sort of seeded rock.
I plan an extra water change on the 90 while it's sumpless and skimmerless.

So what am I not thinking about here, that's going to make life difficult?? :)

the only thing im concerned about is if the 180 does a cycle spike the live rock in tubs may have die off or may not.. i would hate toseeyou lose fish due to a cycle spike.

i could be wrong tho.

The rock in the tub should be stable, it's been in new SW for a month, heated, with fish food added every now and then to build bacteria. I figured 2 weeks to build it up to where it would be sufficient for the livestock to move over, follwed shortly after by a good water change.

I just went from a 55 to a 135. I set up a water transfer with my 2 tanks at a slow rate for a day, with new tank draining into old sump, and vise versa. I had new sand in the new tank, and wanted to acclimitise everything before the transfer. I moved everything over in about 2 hours, left the old tank setup just in case i needed to move some stuff back.

I showed 0 ammonia and nitrites through the whole thing, i tested every 2 hours for that day, and the next 3-4 days 3+ times a day.

My coral and everything transfered great, everything was open within hours and looking better than ever. I had a pretty light fish load, but none of them where affected it seemed, just more room to move around.

I might use the water from the existing sump (it holds about 60 gallons) but the sand is new, rock is new but partially cured/seeded, some existing rock will move over eventually.
Fish load is medium for 180, 15 fish total. 5 butterflies, a tang, a wrasse, 4 clowns and 3 damsels. Pretty sure I'll need to have new water on hand in case of a spike.

Is it possible to move half of your fish, wait a bit to make sure that everything is ok, then move the other half a week or so later? Or move all or as much of your existing rock over as possible, even if it is only to the sump for a bit. Then you will know for sure that your bacteria will handle your bioload.

Rock in the sump is a good idea, I'll do that.

:thumb:
also FWIW everything I have read suggests that transferring over your old water will do nothing to help out the cycle but it will help acclimate the fish a little better.

Agreed. Bacterial content is insignificant, but chemistry could make transition for the fish easier. I prefer to start with all new water though, as I'm switching salt between tanks.

Can you just move everything over at once? If you move all the water and rock from the 90 over as well you shouldn't have any cycle problems, it's really the same as just doing a large water change. I've done this a few times with large upgrades without problems.