If you're wanting a pair, it's best to get them together. Mine seemed really happy together, but then a couple days later one went missing and has never come back. I don't think he jumped, but I suppose he could have and my dog could have disposed of his remains before I noticed. Lily has been fine on her own since then, so they don't HAVE to be in a pair. Lily seems to enjoy swimming around with Neo the Midas Blenny, except during food time. Then she backs off a bit since he's such an enthusiastic eater. She still gets plenty; she just waits for the smaller bits he misses in his rush to get the big ones.