Originally Posted by MarkW19
I guess all I need in the container with the rock is a powerhead (no heater/filter etc.)?
If you've already had it running with the carbon for a bit, most impurities should be removed for the most part. Water changes and scrubing would have also taken care of it to some degree.
And, for the waterchanges, would it be ok to replace the water with used SW from my main tank (ie. after a waterchange in my main tank), as opposed to new SW?
I would use freshly mixed. It would eliminate the DOC
from the main display as being a possible contributor to your ammonia readings however small the chance.
If after a few water changes with freshly mixed and no ammonia, you know the cause.