[untamed]

I have two tanks at the moment...the 400 (new) and the 30 (4+ years old).

That's the background.

Jason...I killed your stag frag. It RTN'd in the 400 two days ago. In an attempt to save it, I trimmed the last healthy bit off and dropped the healthy bit into my 30 gallon.

That small bit also died...then today, two acros near the stag bit have RTN'd in the 30. The 30 gallon shares only 1 thing with the 400 (RO water comes from the same source). I use different salt brands...30 is kalk based, 400 is reactor based...they are completely isolated from each other.

It would seem that I transferred some sort of coral disease from the 400 into my 30 causing the immediate death of two acros. There are two more acros in the 30 that I want to save...so I fragged/dipped the remaining live corals in the 30 and distributed the frags in various spots in the 400. (distribute the genetic material, so to speak)

I have no idea what caused the original death of Jason's frag in the 400. It was fine for 3 weeks or so. I made a number of system tweaks that I thought caused the death at first...but if it was a system tweak, then how does it transfer to another tank?

I've been doing this for many years now and these are the first corals I've ever lost to RTN...and I'm not really sure what happened.