Some gorgonians feed on zooplankton, some on phyto, and some possibly on both; with Blueberry Gorgonians, the water is a bit muddy.
To my knowledge, the common name Blueberry Gorgonian is used for both
Acanthogorgia spp. (formerly known as
Acalycigorgia spp.) and
Guaiagorgia anas - I can't find any info on the feeding of
G. anas, and I can only find info on the feeding of one
Acanthogorgia sp.;
A. vegae.
A. vegae feeds on zooplankton (it has been documented feeding on both rotifers and Artemia in lab settings), so I'd definitely recommend offering zooplankton, but I'd also personally suggest offering both zooplankton (preferably enriched/gut-loaded) and phyto just to be safe (I'd probably suggest a phyto blend, as there's no way of knowing at this point which if any phyto would be nutritious to the coral).
Definitely leave the flow on and feed the plankton into the flow so that it blows into/beyond the coral; in some cases with filter feeders, trying to feed them directly by blowing the food onto them actually causes them stress, so it's typically better to feed indirectly by putting the food into the flow and just letting the food flow to them so they can catch it at their leisure.
For
A. vegae and a few other gorgonians, they found that it's optimal flow for feeding was ~8cm/second (though it was nearly optimal at 6-10cm/second; 8cm/second meaning that a neutrally buoyant object would float 8 centimeters through the water every second in the flow); the colonies they tested had 63 and 84 branches respectively (so they were relatively large colonies), but they ate ~1,200 to 1,400 Artemia in an hour. As far as I can tell, yours seems closer to ~1/3 to 1/2 the size, but assuming yours eats zooplankton and would have a relatively similar feeding rate, that'd mean that at an optimal feeding rate it would consume ~400 to 600 Artemia in an hour.
So, given the feeding rates above (the last source I've linked below gives polyp counts for the colonies if you want a more specific number to work with for feeding rates), I'd assume that your gorg will probably basically eat as much food as you're willing to throw at it without crashing your tank.
Sources:
Trophic niche theory predicts that species in competition for a limiting resource will evolve adaptations allowing them to consume alternative resources and occupy new niche space. Trophic niche partitioning is often identified by differences in the morphology of feeding structures across...
link.springer.com
Gorgonians, including sea fans, are soft corals well known for their elaborate branching structure and how they sway in the ocean. This branching structure can modify environmental flows to be beneficial for feeding in a particular range of ...
www.ncbi.nlm.nih.gov