Thusly "Bill Stock" Spake Unto All:

The new SAEs seem to be doing a lot of "tail standing", swimming vertically
up and down the glass. I gather this is some kind of food search?

No, they're likely just being their hyperactive selves. SAE's are
hyper, and especially when they're new in an aquarium will they do a
lot of swimming up & down the glass.

Also how few SAEs can I leave in a group.

My experience is that a single SAE is perfectly OK. There's also a lot
less chasing, which any more timid fish you might have will
appreciate.

However, a 10G is really too small for SAE's. I'd recommend a single
ancistrus instead - it grows big too, but it's not as an active fish
as the SAE.