How is the water movement ....
 

... in the ocean during the night?

Do the seas get calmer or rougher during the nigh or does it stay the same?

I'm thinking of maybe adding another pwer head and have it on a timer.

It staaas da same. No mor pwer headds.

The currents remain the same at night.

things change in the sea from day to day (there are storms from time to time), but from what i saw the sea waves are stronger in the afternoon, and by the morning things are calm agan. Depends on the area though. But, i dont think u need such changes in yuor tank.

just remember that once you get below the surface weather really doesn't have any affect on water flow. only in the shallowest of water does wind/waves have any affect on what happens below the surface. I have been scuba diving on a completely flat ocean and when it was pretty rough out, and once you get about ten feet down, you cant tell the difference, so whatever current/water flow is happening is not related to any day/night/weather cycle.

Water flow at surface is often a result of pressure differentials and wind/coriolas

Water flow at depth is often the result of the temperature currents as the water in the north pushes to the south and the water in the south pushes to the north to balance temperature.

Would be interesting to see if their is a magic depth where the majority of surface variable disappears and how much the size of the disturbance affects that magic zone.

Would be interesting to see how that affects the design of our flow in the tanks and put some real data behind when laminar vs. chaotic random water flows would be more appropriate based on the optimal depth the creatures in our tanks live at.

Would also be interesting to see how those flows change with the summer vs. winter seasons.

This is why systems that have a 'night cycle' never made sense to me, except in one respect.

Some systems, like tunze stream controllers, hare a 'night cycle' which lowers the flow at night. This doesnt happen in the wild. The only reason for this is that in the wild, fish can scoot off to some other 'less turbulent' locations to sleep... something they cant do in a captive reef as easily. But on the flipside, the night is when corals feed, and deposit calcium (grow), so you dont want to restrict flow at this time.

My suggestion is to make sure your fish have designated hiding areas with lower flow in the tank, so they can get a good night rest... but keep the flow constant.

Agreed with most of what's been said: there isn't a consistent day/night pattern in water flow over a reef. The lunar cycle and hence tidal flow is very important. Regional and local weather patterns are very important as well. There is a great deal of variation over time (within a day, over weeks, seasons, etc.) but there isn't a distinct day/night difference. Sometimes it's calmer at night, sometimes it's more turbulent and sometimes it's about the same.

The only pattern that is sometimes detectable (though is often overwhelmed by other phenomena) is that it tends to be least windy in the early morning and hence waves tend to be smallest in early morning (though not always due to the above factors). Waves only dominate the water flow over the very upper portions of most reefs though, and hence water flow is usually not related to wave action over much of a reef.

I see no reason to reduce flow at night, and in fact, if anything flow would ideally be stronger at night to ensure sufficient O2 transport to corals and other organisms.

Also, as a small note, corals calcify continuously, not just at night. Zooxanthellate corals tend to calcify substantially faster in the light than the dark (usually a 2 - 3 fold difference, though it varies tremendously). Exactly which factors lead to the difference is not understood (lots of hypotheses have been proposed but nothing conclusive has been demonstrated). Nonetheless, it is very clear that corals DO experience maximal rates of calcification during the day and minimal rates in the early morning, before sun-up.

Chris

If you go diving most of the nicer reefs are at some sort of depth. Like 60ish feet and below (now of course there are others shallower) and at this depth waves on the surface make little difference. Or if there is a shelf the top will have the wave action and the shelf will have a linear flow. I don't think having a powerhead on a timer would be a bad thing though maybe you could have one come on at night and one during the day pointing in different directions just to mix it up. It will not be a big factor though.