Why do SPS start RTN overnight?

[Philwd]

rather than during the day? This seems to be my experience and I've read of enough other experiences to believe it's not coincidence. I haven't found any previous discussions about this before so wondering if people have any thoughts as to why? If it's parameter related what's different at night aside from ph? If bacterial related same question.

[hyperfocal]

One possibility: pH and dissolved oxygen often drop overnight; those changes could be the straw that breaks the proverbial back of an already declining coral.

[Philwd]

Yeah I thought of that but was wondering if there was another trigger. Something we could use to help prevent the RTN from starting.

[seapug]

I went through a major RTN event last summer that took out all my acros over a period of about 2 weeks. My tank was going through a generally rough period at the time-- it was pushing 85 degrees during the day and I had a major hair algae (phosphate) problem that I could not control despite twice weekly water changes and vigorous manual removal. It was hella depressing to watch.

Enter the Phosban Reactor+GFO and large fan. 6 months later my tank is back in tip top shape and I've rebuilt my acro collection.

I really think Phosphate + high temps was the root cause of the RTN in my tank. Getting those two factors under control seemed to be the key to solving the problem for me.

[Philwd]

I agree there are factors which cause RTN. But it seems more likely to start overnight than during the day. It will progress during the day certainly. But always seems to start during lights out. Maybe if we knew why we could supply that something that's missing to help the corals get through those rough spots. Whether it be oxygen, higher ph, shorter/multiple dark periods or something else.

[hyperfocal]

Don't discount observational bias; you may just be prone to noticing RTN first thing in the morning, and are assuming an overnight effect.