Anyone else turn powerheads off at night?

[gordongregory]

Am I the only one who does this? Is this a bad idea? My tank contains lps and sps.

[skabimini]

Why? current continues to flow in the ocean at night as well... keep it natural :)

[Anemonebuff]

I think that at night it is best to keep the flow up. Less flow=less gas exchange. Less chance of detrius being suspended.

[gordongregory]

I thought maybe everything could use a break. My return pump from the sump never stops so I thought just a little decreased flow might mimic slower ocean currents at night. Maybe I'll rethink this.

[Zoalander]

It's probably one of the worst things you can do, especailly if you have tangs. You need more oxygen in the tank at night then when the lights are on. Your corals and fish will never need a break from water movement.

[taku]

My opinion is the seas are less rough at night... so I have my power head controller setup on "night mode" just before the lights go off every night. The controller turns less power heads on at a time when on night mode.. so there is still flow from PH's and the return pump, but just not so many PH's on at once to give a little rest. The fish have their hiding places in the rocks so they don't care about flow... and the coral that put their tenticles out at night also don't care it seems... so long as there IS flow, and it's not blowing the meat off the skeletons :p

[fuzz1974]

Who said the ocean currents slow down at night? I would love to read this somewhere. I didn't realize the ocean had a watch, and could tell it was dark. I am talking about the body of water not the animals living in it. So then theortically all the wind stops blowing at night time to? It must to have an impact on water movement. The currents in the ocean have probably been the same for a 1000 yrs. They just keep on moving regardless of day or night. I didn't mean to get sarcastic in this post, but come on man, think this through.

Fuzz

[143gadgets]

I agree. Keep the flow up!

[davidryder]

wow... lighten up haha... currents stay relatively steady but do fluctuate. the season, temperature, moon phase, etc... all affect the motion of the ocean. you think currents stay the same in hurricane conditions? the ocean isn't quite that predictable. the only effect it could have is the O2 depletion. In low light, oxygen is replaced by CO2 more rapidly and the more turbid the surface of the water is the more gas exchange there is going to be. :-)

[taku]

<a href=showthread.php?s=&postid=6845223#post6845223 target=_blank>Originally posted</a> by fuzz1974
Who said the ocean currents slow down at night? I would love to read this somewhere. I didn't realize the ocean had a watch, and could tell it was dark. I am talking about the body of water not the animals living in it. So then theortically all the wind stops blowing at night time to? It must to have an impact on water movement. The currents in the ocean have probably been the same for a 1000 yrs. They just keep on moving regardless of day or night. I didn't mean to get sarcastic in this post, but come on man, think this through.

Fuzz

Nice try, but actually reefs are more calm at night. Reefs are in shallow water (comparitively speaking) and winds drive surface currents which affect shallow water inhabitants. Winds are calmer at night. Wind obviously doesn't affect deep water currents but that's not where the reefs where our animals came from sit anyways. If you would like to read more to educate yourself you can google search ocean surface currents.

"Surface water movement takes place in the form of currents. Currents move ocean water horizontally at the ocean's surface. Surface currents are driven mainly by the wind."

Thanks

[uscgbeachbum]

taku is very correct on this one. In general, waves do calm down at night due to less wind. However, the decrease isn't extremely drastic. The drop (at most) is about half. Obviously, this all depends on water depth. Some reefs are in 80 ft of water while others are at 30 ft. The change will be more pronounced in shallower waters due to wave interaction. Of course, the likeliness of anyone having a "geographic-specific" reef is extremely slim to none. I have done LOTS of field work with ADCPs and I have proof if anyone requires.

[Craig Lambert]

Waves calm down, but tide forces do not. If you look at any tidel chart you will see that the highest and lowest tides rotate around the clock throughout the month. Tide forces is what we are trying to simulate, not surface action.

[Crusty Old Shellback]

I haven't done any reasearch on it but have spent 21 years sailing around the worlds oceans. :D The water does normally tend to quiet down at night. There are circumstances when it dosen't like during storms. But then again, I've seen the oceans just as smooth as glass during the days as well. ;)

For me, I have two hammerhead pumps running my system, one on my sump return and one on a C/L with a swimming pool canister filter in line. I shut down the C/L pump at night when the lights are out. The canister filter is used mostly for removing the fish poop from my large tangs. :D

One thing I've noticed on my tank, when the lights go out and the pump stops, the fish all go to their "beds" and tuck in for the night. Even when I shut down the C/L for filter cleaning, they will go to their "beds" for a bit as they think it's night time. :lol:

[moogoomoogoo]

I don't have any scientific data. But based on my experience SCUBA diving, currents always appeared less strong at night.

[uscgbeachbum]

Just in case someone doesn't know what an ADCP is...ADCP = acoustic dopler CURRENT profiler. The ADCP measures water currents with sound, using a principle of sound waves called the Doppler effect. A sound wave has a higher frequency, or pitch, when it moves to you than when it moves away. You hear the Doppler effect in action when a car speeds past with a characteristic building of sound that fades when the car passes.

The ADCP works by transmitting "pings" of sound at a constant frequency into the water. (The pings are so highly pitched that humans and even dolphins can't hear them.) As the sound waves travel, they ricochet off particles suspended in the moving water, and reflect back to the instrument. Due to the Doppler effect, sound waves bounced back from a particle moving away from the profiler have a slightly lowered frequency when they return. Particles moving toward the instrument send back higher frequency waves. The difference in frequency between the waves the profiler sends out and the waves it receives is called the Doppler shift. The instrument uses this shift to calculate how fast the particle and the water around it are moving.

Sound waves that hit particles far from the profiler take longer to come back than waves that strike close by. By measuring the time it takes for the waves to bounce back and the Doppler shift, the profiler can measure current speed at many different depths with each series of pings.

The same ADCP can also measure wave information such as height, period, and direction.

[Crusty Old Shellback]

uscgbeachbum,

Nice explination on Doppler and the doppler shift. ;) I've been working with CW and doppler radar for years. ;)

What kind of frequienceis are you guys using? I'm assuming it's at least above 22K as you said it can't be heard by humans.

I didn't know there was anyone doing studies like that. Sounds interesting.

[uscgbeachbum]

The range of frequencies is quite large. It also depends on the ADCP manufacturer. If I had to guess, I'd say it the lowest freq was 25k. We do ADCP modeling for lots of projects. The most recent one being on Anguilla for an extremely upscale resort (up to 150k per week) who is looking to do some expansion. I get to travel all over the world to various reefs. Its great. :)

[Crusty Old Shellback]

Is there a upper limit for the frequiences when using them in water? I thought that there was as that's why teh Navy's use the lower frequiences.

Sounds like a fun job. get to dive much on the trips?

[nemofish2217]

i think a point that needs to possibly be made, is that while the current might calm down some on a reef at night...there is still plenty of gas exchange and therefore oxygen to go around... When you have a decently stocked tank, oxygen is depleated much faster....so, while i would say that it is fine to reduce powerheads maybe a little.... you cannot compare your tank to the ocean......so, IMO, i would keep the flow going pretty significantly... just my .02

[RichConley]

Nemofish, current in our tanks in most cases does little for gas exchange. Surface distrubance is what does it, and the in-tank pumps, and closed loops, generally add very little to surface disturbance.

[nemofish2217]

so, are the skimmers what produce most of the oxygen in the tank? i guess i was thinking that when the water crashes down in the sump, and goes through the skimmer, a the amount of oxygen mixed was sufficient..... is this true? If it is, then in that case, would it be more correct to say that you shouldnt turn of your return pumps at night?

[Crusty Old Shellback]

That sound sabout right to me. I only turn off my C/L which dosen't enteract with the surface anyways so thete is no way to add and gas exchange. My skimmer and sump return run 24/7 other than cleaning. I have a hammerhead for a return pump, 5000 GPH so I'm not worried about losing the gas exchange by shuting down my other pump.

However, a lot of people do not run as much water thru their sump as I do so they may be concerend about shuting dwon a PH that may be agaitang the surface water. ;)

On my smaller tank, 45G I do not shut down the PH's as I don't have room for another timmer on that system. Plus there is not as much of a Poop load or high flow on that tank. ;) It's a LPS, shroom, zoa tank.

[nemofish2217]

what dimensions are your 45? i have one, that is about 24x24x18, and i was looking to maybe to get it replaced because it is old, has scratches, needs to be replaced... so if your tank is the same dimensions, where did you get it and who makes it?

[Crusty Old Shellback]

My 45 is a hex tank that I've had for about 10 years. It's been a reef for about 7 of those years. It's glass but does have a few scratches in it. Some pic's of it are in my gallery. ;)