I caught him eating it just a couple of minutes ago! It's pretty hilarious to watch, really, but I was impressed to see him actually eating it.
Sadly I lost one of them - I think I had some water quality issues after I did a large water change, and some of my ember tetras got fin rot and/or fungus (all getting better now), and one of my SAE died. Hopefully I can get another some time soon, but I'm glad that the remaining one is doing fine, and I seem to have found the problem. Such a shame though, whenever a fish dies of anything but old age.