Low flow at night?

[david.faik]

Planning flow in my tank.

Was wondering why I read everywhere that people lower their flow at night. I even read stuff about fish sleeping, which seems odd as the ocean doesn't flow low at night for the fishies.

Basically I was thinking of doing the reverse. I like a period of lower flow in the day, as the corals really extend and stretch. Plus it's pretty mellow.

Then at night the corals are not out anyway, crank things up for a period for nutrient export. So seems to me this would be the best time to pump up the jam and kick some crud around with high flow, being as the corals are retracted?

Maybe someone can share their thinking on flow rates night and day, or why doing the opposite of what seems the norm might be bad / dumb idea?

The only thing I can think of is that fish find low flow areas to sleep in the wild, which they can't much do in a glass box.

Thanks for your thoughts!


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[karimwassef]

High flow is not good for coral. Most will retract their tentacles - counterproductive at night.
Low flow is not good for coral. Detritus will settle and bacteria will build up, algae, etc...
Changing flow that comes in from many different directions & varies over time is good. Balance is best.

Day or night doesn't matter if the flow is healthy.

 

[slief]

I lower my flow at night on my Tunze's and my closed loop pump so the fish aren't dealing with the higher flow when the rest. For that reason, it's also a good time to save energy since we pay though the nose for kW here. My power usage is already high enough because of the tank. Any opportunity to save money in that regard without it being detrimental to the tank is welcomed by me.

 

[davocean]

Actually I don't think many do lower their flow at night, though this question is often asked, and I agree, as a long time diver I can tell you the ocean certainly does not have less flow just because it's night time, in fact many times I observed the opposite.

The wind often dies down at night giving the appearance the ocean has calmed.

Our small systems actually benefit more by having the flow constant, and especially at night w/ lights out.

As to coral polyps needing a relaxed period, that I agree to, and why many of use choose to use random flow or wavemakers.

 

[VGT]

I put my MP10 into night mode, everything else is the same though.

 

[DrewCam]

yea, for me its just another way to add some variety to the flow in the tank. Day or night probably doesn't matter but the fish might rest a little easier with less flow. Otherwise, a reef tank with constant high flow doesn't provide a lot of opportunity for good rest for your fish.

 

[karimwassef]

That goes to structure. Fish need safe areas to rest... caves, nooks, ledge overhangs...

I ran a surge at night every night for a few weeks to test. I turned off the low level powerheads that pump through the rockwork. The fish found their safe zones and were fine, but you need to plan ahead.

 

[homer1475]

I run lower flow at night but only by 20%. It has nothing to do with allowing the fish to rest, they will find caves and such in the rockwork for that. My reasoning is I feed my corals at night when their tentacles are out and the slightly lower flow allows then to grab the food instead of it being blown right off them.

 

[Dans85]

I have actually seen the opposite with polyp extension, specifically with acros. The flow is the same night and day, but I've noticed that during lights out my acros extend their polyps quite a bit more than during the day.

 

[karimwassef]

Usually fear of predation drives them to retract during the day, but your tank may be different.

Also, your plankton or food base may be plentiful by day and they can smell it.

 

[ktownhero]

Real reefs are enormous with all sorts of different nooks and crannies for fish to hide from flow to sleep. An aquarium isn't big enough to provide that, so we can facilitate that by lowering the flow a bit at night. But not so low that it's bad for the corals.

If you dive on a real reef at night you see almost no fish. They are all hidden inside the reef.

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