Zoanthids get most of their energy from light, but light feeding can speed growth and help colonies recover.
Zoanthids live mostly on the sugars their symbiotic algae produce, and many tanks grow beautiful colonies without ever feeding them directly. Even so, zoas do catch small particles from the water, and Palythoa take food much more readily. Feeding is a useful extra, not a requirement.
When feeding helps
- New frags recovering from shipping and dipping
- Ultra-low-nutrient tanks where colonies look pale or have stopped growing
- Palythoa, which are more active feeders than most zoas
- Grow-out tanks where you want faster coverage
If your colonies are open, colorful, and growing, you may not need to feed them at all.
What to feed
Zoanthid mouths are small, so food needs to be fine.
- Fine particulate coral foods
- Rotifers and copepods (live or frozen)
- Cyclops and other small frozen plankton
- Fines from thawed mysis shrimp, rinsed first
Large chunks of food mostly go uneaten and end up as waste.
How to target feed
- Turn off or reduce pumps for about 10 minutes.
- Mix a small amount of food with tank water in a cup.
- Use a pipette or turkey baster to release a gentle cloud just above the colony.
- Watch the polyps. Feeding colonies close around the food or curl their tentacles in.
- Turn flow back on and let the system clear any leftovers.
Once or twice a week is plenty for most tanks. Broadcast feeding the whole tank also works, but it takes more food to reach the corals and adds more to the nutrient load.
Don't overdo it
The most common feeding mistake is too much food. Uneaten food breaks down into nitrate and phosphate, which feeds algae and cyanobacteria. Those can smother the polyps you were trying to help. Signs you're overfeeding include:
- Cloudy water after feeding
- Rising nitrate and phosphate readings
- Algae or red slime appearing on or near colonies
If you see these, cut back the amount or frequency first.
Feeding and fish
In mixed tanks, fish often steal food before it reaches the corals. Feed the fish first, then target feed corals once they've settled down. Some fish, including certain angelfish and butterflyfish, will nip at zoanthid polyps. If colonies close up every time you feed, watch the tank for a few minutes to see whether a fish is the cause.
Nutrients in the water count too
Zoanthids also take up dissolved nutrients directly from the water. In a tank with fish fed generously, low measurable nitrate and phosphate may already be feeding your colonies, and extra coral food adds little. Use test results and colony appearance to decide, not a fixed schedule.