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What's the ideal PAR range for Zoanthids? I've got mine under 150 PAR but they're not opening up like they used to. Tank's a 40-gallon breeder, running two AI Primes, salinity at 1.025, temp 78°F. They were thriving a month ago but now they're acting weird.

150 PAR should be fine for most Zoanthids, but it depends on the species. Some prefer lower light, around 100 PAR. Have you checked for pests? Flatworms or nudibranchs can cause them to stay closed. Also, how's your flow? Too much can stress them out.

Yo, bump that light down to 120 PAR and see what happens. Mine were pissed at 150 too, chilled out when I dialed it back. Also, check your alk, bro. If it's swinging, they'll sulk.

I've had similar issues! My Zoanthids closed up when my nitrates spiked. Are you running carbon? Sometimes toxins build up and mess with them. Also, how often are you feeding? They might just be hungry.

CoralTide wrote: ↑Sun Jul 27, 2025 6:34 pm Yo, bump that light down to 120 PAR and see what happens. Mine were pissed at 150 too, chilled out when I dialed it back. Also, check your alk, bro. If it's swinging, they'll sulk.

Solid advice. Alk swings are brutal. Starwee, what's your alk sitting at? If it's not stable, that's your issue. Mine like 8.5 dKH, but consistency matters more than the number.

I keep mine at 130 PAR and they're happy. But lighting isn't the only factor. How old are your bulbs? Spectrum shift over time can affect them. Also, what's your photoperiod? More than 10 hours might be too much.

Mine do best at 110 PAR, but I've got a mixed reef so I can't go too low. You running any supplements? Iodine and amino acids help mine stay open. Also, what's your Mg at? Low Mg can mess with polyp extension.

thart wrote: ↑Sun Jul 27, 2025 6:12 pm 150 PAR should be fine for most Zoanthids, but it depends on the species. Some prefer lower light, around 100 PAR. Have you checked for pests? Flatworms or nudibranchs can cause them to stay closed. Also, how's your flow? Too much can stress them out.

Agreed on the pests. Starwee, dip them in coral rx just to rule it out. Also, how's your phosphate? High PO4 can make them cranky.

PAR isn't the only thing, spectrum matters too. Blues vs whites can change how they react. I'd try reducing whites if you're heavy on them. Also, what's your calcium at? Mine like it around 420.

I'd start with a water change. Sometimes it's the simplest fix. Also, how's your tank's bio-load? Overstocking can lead to stress. What fish are in there? Some species nip at polyps.