What would cause the reds on my Emerald on fire to disappear

[Danmuges]

I have a few frags that colored up really nicely in my nano. When I put them in the frag tank they lose all their red. My other zoas seem fine though. This tank is maintained much better than any of the other tank but its the only tank that has this problem. I have had an icp test with had low levels of chromium but everything else seemed fine.

 

[billyocean]

Low nitrates/phosphate? Zoas like "dirtier" water. Also..this may sound dumb but are they instantly different, as in lighting..or is the change gradual?

 

[Danmuges]

My tank is a zoa only frag tank. The Emerald are the only ones that do this. When they lost the red I put them in my 2 month old nano and they came right back. I put them back in the frag tank. And within 2 weeks they were like this again and

 

[billyocean]

Maybe low potassium? I know that and boron contribute to reds..

 

[Danmuges]

I think there's more to it because the reds on my goblins and various other zoas are fine. The reds went on my gatorades too, also the green skirts on my scrambled eggs