Identifying the source of coral irritation

[wavy_b]

I've got a mixed tank going on with Zhoas (green and brown), ricordias (6 of them), mushrooms (4), two different torches, one hammer head, acropora with montipora, and just added a RBTA. Every day when I get home from work, my hammer head, torches, and new RBTA are irritated and deflated, showing their skeletons. It's like clockwork, same time every day. During the day, all my corals are looking good, so I'm trying to figure out what's upsetting them.

My water parameters are:
- Nitrates: 2-5
- Nitrites: 0
- Calcium: 450
- Alk: 9.1 dKh
- Magn: 1350-1450

I'm running BML lighting - two strips, superActinic and Full spectrum - from 9am-9pm. Maybe I'm overdoing it with the light and they're getting tired by the end of the day?

Here are some pics of my corals during the day and when they're upset:
RBTA
ZHOA GREEN
BROWN
Hammer
And this is what happens when they get irritated

Any ideas? It's always around 6-8 pm, and by morning, they're thriving again.

[talonix]

Not a stupid question at all, I'd actually appreciate any idea. Have you considered the possibility of temperature fluctuations? It might be worth checking if your tank's temperature is spiking around 6-8 pm, maybe the heater's kicking in during that time?

[wavy_b]

Not a stupid question at all, I'd actually appreciate any idea. Have you considered the possibility of temperature fluctuations? It might be worth checking if your tank's temperature is spiking around 6-8 pm, maybe the heater's kicking in during that time?

Temperature's always stable, 79-80, and if the heater failed, it'd be at random times. This issue's consistent, every night between 7-9 pm. I'm starting to think my Zhoas might be releasing something that's irritating the other corals. Could that be possible?

[brixo]

I'm thinking it's related to the lighting. When do you switch off the day lights, and do you have any kind of transition period before the night lights kick in?

[sweetie_22]

I'm thinking the photoperiod might be too long. I mean, 12 hours of light is a lot. Maybe they're just getting tired. I've seen Euphyllia form bubbles over polyps that are about to divide, so that bubble on your torch might be a good sign. My hammer used to do the same thing.

[finleyd]

I've noticed my Bubble Coral retracts when it's had enough light for the day. If your lighting schedule is consistent, it's not surprising that your corals would retract at the same time every day, given they're getting the same amount of light daily.

[savannah]

I had a similar issue with my frogspawn and torch, they'd deflate at the same time daily. I think it was due to the photoperiod, I had the lights coming on too early in the morning. I changed the timing, lights come on later now but still go off at the same evening time, and now they stay full throughout the day.

[wavy_b]

I'm also considering my fans as a potential cause. I have them set to night mode and I think when they switch over, the change in pattern and power of the current might be upsetting my corals.