"White fungus" normally happens due to a lack of water motion or an injured polyp/colony.
Some times dead organisms around the polyps could develop that too!! When sponges grow around the bases of the polyps they need to be abele to survive. Dead sponges could lead to fungus' growth and therefore spread to the polyps. Sponges normally die because of lack of food and elements (filter feeders) and/or water flow. They die during shipping too, so it's a good idea to check for them when the new frag or colony arrives, prior to introduce into the system.
I found the regular use of iodide, amino acids, vitamins and trace elements (water changes are normally enough!!!) could help some of the species of sponges in closed systems. There is so much more to sponge keeping and I really can't go deep into it because I'm not an expert. I'm not an expert in zoas either!!!
It would be good to search, if you're interested! Other very wise option would be to prevent the growth of any sponges in the system, if you're really concern about them dying among the polyps.
Other times, after years free of "fungus disease", the tank could manifest it after an accidental injury to one or more of the polyps.
I've had that "fungus disease" when the system got to a type of stress too, like changes in salinity or alkalinity, with a high organic content. The areas with slow water motion will develop the disease faster!!!
Some of the dipping treatments I've heard that could work against it are with: Lugol's solution, strong iodine tincture, hydrogen peroxide, Maracyn 1 and Furan 2. But you can do only with the frags. Please don't use any of these in the tank. It needs to be in a dipping fashion. Make sure you're dipping properly. Search for dipping practices for zoas.
I normally use Lugol's solution: 8 - 10 oz of tank water (or fresh water) for 3 - 5 drops of Lugol's solution for 3min. Iodine tincture could be used also in the same rate.
Yes, temperature could help to prevent/slow down the disease. In systems with temp. between 75°F - 79°F should be less prompt to develop the disease.
Normally the polyps begin to develop the "fungus" from their bases and some of the times they detach from the rock ending up all around the system. Some other times they just waste away turning dark gray or black, shrinking/melting. I believe the tow forms to be different pathogens. I also believe there is more than 1 type of "white fungus disease", showing different speed rates and different types of structure. Some are more white than others too.
We don't really know if the "white fungus disease" is really fungus. It could be a bacterial infection, but it's called "fungus" because of it's appearance. I don't know of any scientific proof that would say it's really fungus after a microscopic examination, to this date.
Best way to avoid that is to prevent introduction of the pathogen in the system, dipping every new colony in Lugol's solution. Some say Coral RX is a great preventive dipping solution also. Please keep in mind that even another type of organism, live rock or even plain natural sea water would be enough to introduce any microscopic pathogen to the system.
A good water flow will be one of the best things you can offer your zoas!!! To dip and quarantine the new zoas is the best way to deal with the problem, eliminating great chances of having it!!
The type of fungus found in zoanthids are probably basically the same that live rocks will have when there are dead organisms in it, like for example sponges or some type of algae. The smell is terribly rotten.
I just wanted to participate in this thread...
Stay safe and keep zoaing!!
Grandis.
