So—you’ve received your zoas (hopefully from Zoanation 😄), followed the acclimation guide from our listing, and placed them into your tank.
Now what?
How do you know if they’re actually happy in that spot?
This guide will walk you through how to visually assess your zoas based on three key factors: flow, light, and water parameters.
Flow (the stronger, the better?)
Flow is the easiest factor to judge.
In the wild, zoas are often collected from shallow, high-wave environments, so it’s almost impossible to give them too much flow in a home aquarium. That’s why in our listings, most zoa strains are recommended intermediate to strong flow. Sometimes you might notice that a zoa placed too close to a wavemaker doesn’t open at first because it’s being blown around, but after a night of adjusting, it usually opens up. In general, when a zoa is in good condition—polyps fully open, tightly attached to the base, and lashes moving naturally with the current—stronger flow is better.
(Picture is a new unnamed strain we are growing!)
It improves both food capture and waste removal. Personally, I also think this is why high-end zoas are less likely to suddenly “melt” under stronger flow. The only thing to watch out for is that new frags that haven’t properly attached yet can easily get blown off and drift around the tank (though Zoanation frags are all well-rested).
Light (a relative factor)
For lighting, if you have a PAR meter, you can simply follow the PAR requirements listed for each strain. But if you don’t, you can still judge things by eye. There are two key acute morphological changes to watch for.
The first is “umbrellaing.” This is when the center of the polyp flips outward, the lashes turn downward, and the whole polyp starts to look like an umbrella. This usually indicates that the light is too strong, and the zoa should be moved to a dimmer area.
The second is “long stemming,” where the polyp stretches upward—pretty self-explanatory. This means it’s reaching for light, so you should either increase the lighting or move it to a brighter spot. That said, some varieties, especially palys, naturally have longer stems, so they may still appear this way even after being moved.
Both umbrellaing and long stemming are acute and reversible, and in most cases the zoa will return to normal within a few days after being repositioned. However, if left long-term, excessive light can lead to bleaching, while insufficient light can cause the coloration to darken—both of which are much harder to reverse. We’ll go into more detail about this in a future article on zoa diseases.
It’s also important to understand that light intensity is relative. A zoa that has just been shipped, is stressed, or has been kept in a low-nutrient environment may start umbrellaing at around 120 PAR, but after gradually adapting to your tank, it may tolerate 200 PAR and even develop brighter coloration. Zoas can grow well across a fairly wide range of lighting, but generally, the higher the light they can tolerate, the better and brighter their colours will be.
Parameters (stability over numbers)
As for parameters, there isn’t too much to cover—the main ones to watch are PO₄ and NO₃. Ideally, PO₄ should stay between 0.03 and 0.1 ppm, and NO₃ between 5 and 50 ppm. Like other corals, slightly higher nutrient levels allow zoas to tolerate stronger lighting, but if they get too high, they can become toxic and lead to issues like infection and melting.
For more sensitive, high-end strains, you should also keep an eye on KH and pH. The key thing to remember is that stability matters more than hitting exact numbers. Frequent fluctuations are far more likely to cause problems than values that are consistently a bit high or low but stable. Don’t chase numbers—let your zoas adapt to a stable environment.
Thanks for reading, and we hope this helps your zoas settle in and grow quickly.
Dr. Chen
Zoanation