Hello Jenn,
I have very little experience with this; our systems have traditionally remained largely free of Bryopsis, and when I have had it present in a system it has been eaten by the resident herbivores (usually an assemblage of surgeons and damsels). The person that tends the reef aquarium at the Smithsonian used our Magnesion-P to eliminate Bryopsis they had in their systems; as I recall, he maintained the [Mg2+] in the realm of 1,700-ppm for an extended period of time and the algae eventually began to turn white at the tips and die back. I can tell you that there are plenty of surgeons housed in that particular system, and that they didn’t noticeably touch the algae, however that tank is also heavily-fed and the fish are not forced to forage as much as they have to in our systems. The specific surgeons that I have had eat Bryopsis are Sohals, and our Azure Damsels have also shown an interest in that macroalgae. Of course, neither of these species would be considered “nice guys”, but they serve a function and as such are welcome inhabitants, obnoxious as they may be.
Regarding the theory that elevated sulfate concentrations impact the Bryopsis, it’s hard to say whether that would be the case. The [SO42-]NSW is ~2,711 ppm, which is relatively high when compared to all other anions save chloride. Perhaps the fact that sulfate is divalent enables it to interact with multivalent cations that Bryopsis requires for normal function (e.g. iron and manganese). Why this would impact Bryopsis and not other forms of macroalgae in the system is impossible for me to say; it would have to be something specific to Bryopsis and closely-allied species for this to be the case. Not being much an authority in the biology of algae, I can’t offer much more light on the subject, I’m afraid. For what it’s worth, I would tend to believe that in order for copper derived from magnesium supplements to have enough of an impact on algae, it would also have a nasty impact on sessile invertebrates; for instance, I’d expect snails to start dropping dead if the copper concentration was elevated. I could be totally wrong, as stated, since I’m not well-versed in the specific biochemistry at work here.
Kindest regards,
Chris
CR Brightwell