Butterflies or gobies?
My butterfly went through cupramine with no issue.
How do the three Rainfordi deal with being a trio. I've not heard of keeping them in groups before, but I've thought about getting a second one for my current specimen.
Are they eating for you yet? My Rainfordi and my Sunburst butterfly were both tricky to get eating. I had to use a fresh live oyster to finally get a feeding response.
Hope they work out for you.
Good luck! Keep us posted, and keep an eye on the chasing... it can get bad very quickly. I've never seen more than one in a tank long term.