Zoanthids cause of decline.

[Dbigfish]

June of 2019 i had to move and instead of moving the old 13.5 fluval nano tank i took the opportunity for a slight upgrade to a 20 long with a similar filtration style.
The new tank had the same brand of crushed coral substrate and went from a current orbit marine to the same brand newer model one size larger. I could never achieve the same visual look but I programed it to similar % across its channels and kept the lighting schedule the same. All filter media from the old tank and rockwork from the old tank went into the new tank.
The first picture was taken 3 days after the move and everyone seemed to have adjusted well. The other pictures were taken 2 months in. There had been no new growth in the new tank but everyone was still out and eating (reef roids). Then my bucket of instant ocean salt ran out and I decided to get the instant ocean reef crystals with plans to do more lps coral (I had a healthy acan and duncan). 4 months later and all the zoanthids had disappeared except for one small colony. That little patch remains today, my clownfish murdered my acan and duncan both and in my disappointment I have given the tank over to gsp.
Could the salt really have done all the damage? I got it right on accident in first tank failed on the second and would like your opinion before the third(40 breeder)

 

[Sniperhank]

Something else is going on. I'm shocked that you were keeping LPS under the stock lighting with any type of success. There is a chance, and more likely scenario, that the rock wasn't rinsed at all and brought over loads of the build up from the old tank and a parameter spike caused the die off.

 

[Dbigfish]

I did mention light on the original 13.5 was a current orbit marine light I never used the stock lighting though I probably worded it strangely. My acan grew 6 new heads under that but then declined in step with the zoas. Its true the old rock work was just transported in buckets direct from the old tank in a half hour car ride i didnt was them. I'm fairly colorblind and the nitrate test on my liquid test kit is the only one I can really make out so my water changes were based off that alone.
I'm set to move again in a year and just want to have a more visually interesting tank. My inhabitants ( black and white ocellaris clownfish, yellow clown goby, and cleaner shrimp) are all happy and healthy my shrimp molts very regularly but the tank just isn't at all what I want it to be an i dont really know how to steer is in the right direction.
There is a small protine skimmer that does its job and i run a bag of chemi pure in the back chamber.

 

[bribo12]

You may have had a small spike from moving the rock work but zoos can be pretty tough. The one thing I’ve seen that makes zoos melt is a sudden change in alkalinity. Do you test for alk with a decent kit?

On the more interesting tank there are some nice goniopora strains in the hobby now that are aqua cultured and do well with not that much lighting. They add color and movement. I really like ricordea mushrooms too as they are super colorful but don’t get as crazy out of control as a lot of other shrooms. Finally, I love rock flower nems for color. If you can imagine a color combo they come in it and they don’t move around like bubble tips or get nearly as big. Perfect for a nano

 

[Sniperhank]

If you're planning on moving again, just wait until after the move is done. That makes the upgrade a lot easier. This time just really rinse the rocks well in old tank water before you put it in the new tank. When I did it, I moved them all in 5 gallon buckets of water and did many dunks in the bucket before the final transfer.