It is possible to keep dwarf seahorses (Hippocampus zosterae) in a mini reef in some circumstances. For example, this is what Joanne Heuter reports in that regard:
" I have never kept dwarfs in a reef tank environment, but I have talked to people who do. They tell me that dwarfs are well suited for reef tanks that have less active fish, shrimp, or crabs. The reef should not contain any large sea anemones or the seahorses could become food for them. In a quiet reef with lots of live rock, sometimes the dwarfs can become self sustaining living off the small creatures that inhabit the rocks."
However, you cannot count on adult Pixies or dwarf seahorses to eat frozen baby brine shrimp or any other frozen foods consistently. Dwarf seahorses are pretty lazy hunters. They like to anchor their tails to a convenient hitching post and wait for their food to come to them, rather than chasing after potential prey. In most cases, attempting to get them to eat frozen food just results in polluting your aquarium.
It can sometimes be done with lots of time, patience, and perseverance, and it isn’t really as difficult as most folks imagine to train adult dwarves to eat frozen foods IF you have a role model to teach them. Zulus, tubers, barbs, young erectus, etc. all make great teachers, and most adult zosterae will learn to take bits of frozen mysis or sometimes the frozen form of Cyclop-eeze readily enough with such role models to show them the way. But some dwarves just don’t get it and never learn to eat frozen fodder and, in my opinion, it’s just not worth the effort of trying to train any of them.
Why? Because training adults to eat frozen food by no means frees the dwarf seahorse keeper from the need to hatch out huge amounts of baby brine shrimp every single day. Think about it. Anybody who keeps any amount of dwarf seahorses always has zosterae fry on his hands. The fry need copious amounts of newly hatched Artemia nauplii daily anyway, so it’s simply easier and more efficient to hatch out enough bbs for the adults at the same time. Many hobbyists prefer to raise dwarf fry in the same tank as their parents, so maintaining an adequate feeding density of Artemia nauplii for the newborns automatically assures that the adults are equally well fed. For me, there’s just no percentage in spending a lot of time and effort trying to train adults to eat frozen food when I still have to keep a battery of brine shrimp hatcheries cranked up full blast for the babies anyway.
In my experience, Artemia nauplii are the best food for Hippocampus zosterae in any case. Either 1st-instar nauplii from decapsulated cysts, fed to the seahorses immediately after hatching while the nauplii’s yolk sacs are virtually intact, or 2nd-instar nauplii that have been enriched, make a highly nutritious diet that meets all the dwarf seahorse’s requirements.
Be that as it may, Grant, I don’t think it will be possible for you to keep dwarf seahorses in your 12-gallon Biocube simply because the water current will be too strong for these pint-size pigmy ponies. As you know, the new nano tanks and BioCubes are designed with reef keepers in mind and therefore feature brisk circulation and strong water flow. That’s simply not acceptable for dwarf seahorses. The vigorous water currents will swirl potential prey past them way too fast for them to target and eat, with the results that the dwarfs will gradually starve to death in your reef tank regardless of the type of food you provide.
The Gulf pipefish we discussed in my previous post are much better swimmers and should be able to handle the currents in your Biocube with no problem. And they can often be converted to frozen Cyclop-eze as their staple diet, so you would be better off forgetting about dwarf seahorses for your nano reef and concentrate on the small Gulf pipefish instead.
Best of luck with your 12-gallon reef system, Grant!