I don't think zoanthus,palythoa or protopalythoa benefit from iodine dosing or have a particular need for it. The hundreds of colonies I have do well without it. I've dosed it in the past without any discernable benefit. Zoanthus like light , low nutrient water, flow. and a bit of organic carbon. Palythoa and protopalythoa like to eat zooplankton. Zoanthus don't show much feeding response and benefit from some organic carbon in the water ( ie, mine like vodka and vinegar) to meet their heterotrophic needs.
I think all zoanthids benefit from some organic carbon. I do think that corals and clams also benefit from organic carbon also.
Zoanthids are known not to be found in the wild with much food in their guts and not to grab much food when offered in tanks, I know. That said we would think already they naturally wouldn't live if there was another way to obtain nutrition but through absorption from water and light (zooxanthellae) only, right?
Well, I also see that if they ingest certain foods in closed systems is because that would be beneficial to them, as I've confirmed IME. I believe that the key here is food particle size and type. They ingest small tinny particles.
Have you seen your Zoanthus spp. pooping? That's not from organic absorption only, but particles, if not zooxanthellae (partial/major bleaching).
I do feed my zoanthus spp. colonies and they grab/ingest/digest foods offered. They also manifest better growth, colors, response and reproduction when they are fed. The water flow plays with their healthy as well as all the params and light! So I think in a closed system they actually can take advantage to the food particles in order to substitute their needs for nutrient absorption, which is probably very limited in comparison to their original natural environment.
To me all zoanthids sustain their metabolic needs mainly through the zooxanthellae, but they all need the right sized and type of food particles to fully thrive. To feed is to help. If you don't feed them that's ok, they will still live, as we all know.
I still don't really know how much we should feed them in closed systems, but I know it shouldn't be that much. I target feed once a week only and that's more than enough to me. When you target feed you are offering a lot of particles at once and they will storage that energy until next feeding. Perhaps the ideal would be to target feed them very small amounts every day, but if you have a life...
Bottom line is: if they have mouth is to eat. :idea:
I still don't know why many people say that their zoanthus app don't grab/ingest/digest offered foods. I think they are offering wrong sized and type of food particles.
In regards to iodide, well I do see that soft corals could have benefits from it and zoanthids in general, but the need for supplementation is very low. I noticed that when I stopped dosing iodide in my aquarium the zoas were not as vivid as when I did. I have stopped for 3 weeks to a month to test without changing much with my maintenance and have to attribute to the iodide additions. I believe that with a good skimmer a small iodide dosing would be beneficial, yes. I don't have a hard evidence for what I've observed though. I have not major problems with algae doing that and the coralline algae is great, so...
Perhaps the vodka or vinegar dosing would somehow help in the absence of iodide additions? I don't dose vinegar nor vodka. Never did.
Grandis.
KH as well.
