They do fine, single or in groups. I've never kept them with agressive fish as they tend to be docile, although they are very good eaters. The problem IMO is getting them, they don't ship well, and they tend to damage their sides which can be trouble. If they are local you are in great shape. Also, because of the shape, a 6 inch lookdown is like a 12 inch anyhting else, they have a really tall profile so open space is important.