Hey Arringar,
Derek is correct, I almost exclusively feed the Larry's Reef Services foods, which are a frozen blend of what I think is probably the best all round food on the market. I do occasionally feed PE Mysis, frozen clams on the half shell and Julian Sprung Sea Veggies.
In regards to grating/shredding, I don't typically do that with the clams. If I feed shrimp, which I try to get fresh and unfrozen, never cooked, I like to grate that...and it is a slimy mess.
I'm going to assume that since you mentioned that your butterflies are swimming around with other fish (angels - which ones out of curiosity), that you didn't quarantine them. Everybody has their own philosophy on quarantine vs. not, but in this case, I would probably recommend seperating these fish so that they don't feel pressure from other fish when trying to eat.
In regards to my Altivelis and Collare, up until a couple weeks ago, I was pretty much expecting to lose them. Their appetites weren't where they needed to be, and if I had introduced them into my DT, regardless of disease issues, they just simply wouldn't have been able to compete for food. I'm happy to report now, that because of the quarantine period, I expect to introduce them into the DT in the next month or so.
I use quarantine for preventative treatment of disease, but also for acclimating a fish to captivity and training them to eat and recognize me as the food source. With these two new butterflies, it's taken way longer than expected.
