How abiotic factors affect zoanthid growth
I'm just going to hop right into it. Certain abiotic factors have been shown to affect zoanthid growth through multiple research studies that have been done. I can link the articles in the comments if people are interested to read them. I will break them down for you. It has been shown that higher dissolved oxygen values correlate to higher growth rates on zoanthid species. This means heavier water flow creating gas exchange at the surface aids in zoanthid growth. A step you can do to increase your DO is either add an extra power head or aim your powerhead at a slight angle towards the surface water of your tank. Another correlation to zoanthid growth has been found to be a salinity of 34ppt or higher. This is not crazy new information as most of us keep our reefs around 34ppt. I encourage you to test your zoanthids range. Mine seem happiest in my experimental tank at 1.026.5 so roughly 35.5ppt. This next one is the biggest key for me, elevated water temperature. Almost all of the zoanthids we keep in our reef tanks come from the infralittoral zone and the intertidal zone. These are both 5m or less in depth meaning this water is way warmer than the water your SPS corals are found in. I run all my tanks around 81 degrees Fahrenheit and I see growth rates on some colonies of a polyp a week. When you tell reefers you run your tanks at 81 degrees their jaw's drop. Yes if you have a mixed reef you will have to slowly raise the temperature to 81. However once it is there your zoanthids will thrive. All of these points are science backed research that I am recommending you to test and try on your own to see if they might help you. However if you increase your temperature and do not have your nutrients in check, expect for an algae bloom. Comment below and tell me what you think.