a couple ?? on switching over tanks

[don in mass]

my ? is i'm downsizing and i'm gonna use the rock and half my water from the old tank and i will be putting in new bags of live sand do i still have to cycle or will i have a mini cycle .and how long will live rock with flow and a heater in a barrel last and do i need a light to.thanks for any input don

 

[Conlius]

Live rock will survive in a dark barrel for a long time. Eventually, after a long time (doing water changes every week or two), it will go from algae driven (both good and bad) to bacteria driven. Your coralline algae might die back a bit after a little while though. Pods and the light should live.

As far as the cycle goes...you are going to have a small one no matter what. There will be small amounts of die off during the transfer just from exposing certain things to light and removing them from the water. Stirring up your old sand bed will result in some non-photosynthetic organisms to die immediately when exposed to light. Die off will result in ammonia, nitrite, and eventually nitrate. However, it shouldn't be too bad.

Take the water you aren't transferring, put it in a bucket...and use it to lightly swish your rocks in. It will get rid of some of the "reef mud" that has gotten down into the smaller holes over time.