It's a pair of aquamarine colored Stentor, much like the common brown ones I see by the thousands in my pond filter sponge. Finding a colored pair is a rarity in a backyard fish pond, eventhough there are several colored species. The green color tone in this pair is probably due to the presence of symbiotic green algae. These two protozoa are really no different than any of the other Stentor species. The only difference is their vivid coloring. These two are not really a "pair". They multiply simply by sprouting a new "bud" from the side of the body.