Day flow vs. Night Flow

[reedman]

OK, Time for a new topic to dig into. I was talking with Dave B from O2manyfish.com when he was in the area for a club meeting and were discussing the flow in his tank. One of the things that he said he did was slow the flow as much as possible in the evening (he uses Tunzes to do this, but it could be engineered other ways). He mentioned, and I agree, that the flow in the oceans is not full blast all the time. During the tide changes there is a diminished flow.

Here are a few of the things I'd like to talk about:

1. What is the benefit of reducing flow, weather it be for 10 minutes or 3 hours?
2. Are there any negative effects on the animals (not the equipment)?
3. We have no where near the amount of flow as the oceans do, so does a change from our full blast to very little and back actually do much for the corals/fish?
4. Could this aid in any other areas of husbandry (i.e.skimming, detritus export, etc.)?

Extra reading links would be just as great as intelligent debate/conversation.

 

[Krish]

Really great topic Reed! The one thing I've always wondered is if my fish need a rest at night. Every morning when I go to check on the tank before heading out to work, I notice my clowns are always sleeping at the top of the tank in a corner where there isn't much flow. Sometimes, they even try to wedge themelves between the CPR overflow and the tank wall...Definately, the water tends to be a lot more still in the ocean at night compared to the day from my observations living on an Island. Many times coming back from out in the boat all day, you tend to find the ride back in the evening so much more better/smoother than it was going over about mid day. If you guys need me to conduct a few tests for you like count waves between day and night etc or anything you guys may think would help, I'd be more than happy to. Just let me know...

Great topic again Reed! Hope the thread goes well

 

[reedman]

Also the coupling of feeding at night with lower flow and it's affects on coral/fish feeding.

 

[jlehigh]

IME reducing flow or pausing it for short periods allows sediment caught in your flow pattern or being missed altogether to get a second chance at making it into the overflow regardless of how random your flow is to begin with.

I maintain a random high flow environment yet everytime I turn the wavemaker off for a few minutes and restart it, all kinds of new junk is stirred up and into the water colum.

In a reduced flow environment a few things can potentially happen to the chemistry of your system. Less flow could mean less surface disturbance leading to less water/air exchange leading to lower ORP and possibly PH if you run a CO2 CA Reactor. Not a big deal but at night the ORP and PH reach their daily lowes and I wonder if this could add to the downswing.

Assuming you have sufficient rock work your fish will be able to find plenty of places to duck out of the high flow areas and sleep. Many of our reef fish have bony fins which are used to hold them in the rocks while they rest.

My SPS system has several ployp nippers.. The result of owning (and loving) polyp nippers being polyps tend to only come out at night. Reducing the flow during peak polyp extending times would seem to reduce the feeding opportunity of the corals. I know nocturnal polyp extension among LPS corals is the norm as well. I think it would however be beneficial to pause the flow for a very short period maybe just prior to lights out in order to stir up detritus for the nightly coral feasting.

I think anything that kicks settled crap back into the water column is a good thing and regardless of how dynamic your flow is. Pausing occasionally and restarting that flow will likely pull up and hopefully out additional sediment.

 

[moortim]

I think that any way we can mimic the ocean is better for us overall (except for sheer volume of course ).

For those of us without Tunze's what are anyone's thoughts on how to do this with regular powerheads?

Tim

 

[Krish]

For those of us without Tunze's what are anyone's thoughts on how to do this with regular powerheads?

Tim

If I were in that boat, I'd probably run a series of powerheads on one side of the tank (maybe 2 or 3) blowing to the opposite end of the tank for so many hours and then shut them off and switch it over to another set of powerheads on the other side of the tank (2 or 3 again) blowing across (sort of like switching tide or currents) for so many hours. Then maybe through the night hours, run maybe 1 from each side through the night etc. I think doing it that way rather than putting your powerheads on a timer that switches them every few seconds would be better on the powerhead as some powerheads aren't designed to be shut off and on simultaneously in that fashion. Just a thought

 

[moortim]

Thanks, Krish.

I am trying to reduce my powerheads to just one on each side of the tank so I will have to think about how to do that.

 

[NaH2O]

Great topic! I'm in agreement with jlehigh here. Just a thought or two to add....I would find keeping detritus in suspension for removal would be far more beneficial than allowing it to settle out by reducing flow/eliminating heavy flow at night. I'm not sure how much reducing the flow in my system would change detritus being removed, but I doubt I'd remove as much as I normally do. If I turned off the closed loop completely, and allowed only the return flow, then I would have some serious collection issues. One of the limitations of my system (or any closed system), is waste has to be removed, or else the water will eventually become polluted. Recreating life on the reef would be wonderful, however, in a closed system it is very difficult to accomplish.

I have a different view on pausing flow. Yes, you will settle out detritus in other areas, and kick it back up when the flow is turned on again, however, detritus is still going to settle in the same areas when the flow is back on. I don't see how you would remove any more than you would by keeping the flow going, because the detritus will be pushed back into the same flow pattern, which eventually takes it to be removed (the flow pattern to get the detritus to the skimmer is still the same). Unless you change the flow pattern every so often, and not necessarily the amount of flow.

 

[Krish]

Thanks, Krish.

I am trying to reduce my powerheads to just one on each side of the tank so I will have to think about how to do that.

Not to get off topic so I'll make it quick, but I don't know if you know, but you can get Tunzes with a night sensor that will turn down the flow the minute the sensor senses darkness. There's your night mode and then you can get 1 Tunze for either side with controllers and set them to alternate between the two. So for eg. While Tunze 1 is giving you say 2,000 gph for 10 seconds, Tunze 2 will be set up giving you say 500 gph for 10 seconds and then it switches. Just a thought

 

[reedman]

The engineering of making it happen is the least of my worries. I just wonder how much benefit you get for the effort. It's reasonably simple to set up a closed loop to recyle water in a "loop" outside the aquarium (in plumbing) with a MBV. Not cheap, but doable. Tunzes work as well. So do powerheads on a cheap wall timer. There are a lot of ways to do this. My question is "is it worth it?"

Thanks for all the thoughts so far. I haven't seen any anecdotal information yet. In the wild corals feed primarily at night when the seas are calmer and there are less predators. In our tanks the feed when there is food. Most tanks don't have an appreciable population of predators so the corals are free to feed during the day.

 

[RockyHeap]

For those who think the ocean is calm and sleeps at night, you've never dove on a real reef before.

Everytime I come back from a tropical trip or scuba dive, I always increase current in my tank......my present 135 swirls almost as fast as a flushing toilet goes round and round.

Why is Fiji and the Eastern Carribean so loaded with abundant life? Because they both fringe a major nutrient rich upwelling from the depths that constantly floods the reef with food particles.

In a lagoon system with fringing reef, the currents can easily approach 3-5-6 knots over a reef during incoming or outgoing tides, and no there's not a slack.

I don't think it's really possible to have "too much current" in a reef tank as long as you're not dirrectly blasting the coral 2" from a power head outlet. Indirrect current and constant feeding 3-4 times a day rocks for a healthy tank.

 

[jlehigh]

I have a different view on pausing flow. Yes, you will settle out detritus in other areas, and kick it back up when the flow is turned on again, however, detritus is still going to settle in the same areas when the flow is back on.

Good stuff Niki,

I think my tank is unique, rather folks with OM wavemakers are unique this way. In my tank there are 14 inlets, where four are fed at a time in seven second intervals. When I turn off the pump but allow the OM to continue to turn and then power the pump back on, the direction of the random current changes until the pump and OM have been running long enough to resetablish the repetative pattern.. It's really hard to describe but it has to do with the collision of the currents and the changes that happen when the pump start-up turns on for inlets 1,5, versus 2,6..

I more efficiently change the flow pattern though by changing the OM's drum which changes the pattern the inlets are fed in...

Here is my plumbing diagram (except I recently cut out the spray-bar):

Sorry if this is a deviation..

 

[moortim]

In response to Nikki's comments has anyone tried reducing their flow at night? What effect did it have?
While you would still want a decent flow at night, with the higher flow in the day could you get away with say, increasing the day flow even higher than what you have now and then decreasing it at night to a level, not quite as high as original but still high enough to keep detritus in the water column?
I know it would depend on what the original flow was as well as how much work you wanted to do on your tank but It could be one way to do it.

Tim

 

[reedman]

For those who think the ocean is calm and sleeps at night, you've never dove on a real reef before.

Very true. I was more interested in a "lower flow" time at night. Correct me if I am off base here, but I thought that there was a significant difference in the flow at night vs. the flow during daylight on a reef.

I haven't been diving....yet. My tank is geared more toward the reef crest area so maybe the flow really doesn't diminish at night or during tide changes. This is why I wanted to start the topic.

Thanks for all the info everyone!

 

[Krish]

For those who think the ocean is calm and sleeps at night, you've never dove on a real reef before

I've never been underwater past the time when it gets too dark for me to see what is going on. Nevertheless, depending on what time a year it is, the currents are different. Infact, today may differ greatly from tomorrow so trying to mimic is kind of impossible. Saying a reef isn't calm and doesn't sleep at night is kind of a bold statement. Saying a reef is calmer at day than at night or vice versa is a bold statement as well. Some days the water is AlOT rougher than at night and some nights the water is ALOT rougher than the day. Then you have to factor in Spring Tide which almost brings the water up on to land, hurricanes and all those other factors that change things up a lot and doesn't give you a simple guidline to follow. Simply put best, the ocean is everchanging... It is as random as it can get from what I can see passing by the water everyday on my way out to work and back home and living on an Island my whole life. Yeah nights seem to be more calmer than days if I were to rate the two, but still no necessarily the case. So IMO, slowing down flow on a time table every night is kinda far from the real thing from what I see. I guess if we wanted to really mimic the ocean, then we'd have to have some days with more current than nights and vice versa. Just my thoughts...HTH

 

[reedman]

Good to hear Krish. No substitute for real life observations.

I tend to agree that we will not see much benefit from the low flow/high flow change. Just trying to see what people think.

Dave said that he saw sliming, don't know if that is a good thing or not, but he thought it was. It was just time to get more opinions on the subject and I think I got that.

Thanks all.

 

[Krish]

Good to hear Krish. No substitute for real life observations.

Thanks Reed...Doesn't mean I know what I'm seeing and interpreting it right though(LOL) But on a serious note, the ocean is one serious system. Everytime I go out in the boat or sit on the beach and see really how far the water stretches and all the life forms etc. and then I think about what I have at home, I tend to say to myself, "Who the hell am I fooling"(LOL) In any event, I think the hobby has really come far. Thanks to everyone who has put in the effort to make things a lot easier for us as hobbist

 

[jlehigh]

Hey Reed, Mind if we talk about sliming more?

My understanding is corals slime for both defensive and feeding purposes. Let's talk about slime netting for feeding purposes.. It makes sense to me that if the flow in the tank slows down this would allow coral slime to stay attached to the coral animal, gather food from the water colum, and retract the slime to digest the netted goods... I didn't think about that aspect..

I quite easily get every coral in my tank to slime by letting air into my penductors creating a 280gal skimmer! lol but the flow in my tank just carries the slime into the overflows.

Krish it is great having someone on the boards that can just look in their backyard and make pertinent observations love it..

 

[Krish]

Krish it is great having someone on the boards that can just look in their backyard and make pertinent observations love it..

You're welcomed to hang out anytime time man...Anyone is! I'm not selfish(LOL)

 

[MikeS]

For those who think the ocean is calm and sleeps at night, you've never dove on a real reef before.

I think the goal here is to make the flow varible and random (like the ocean), not necessarily to shoot for a "calm". I do agree with RockyHeap...I've dove alot and most areas the current will move you right along...:lol: On the same note, I've dove areas where the current is reletively calm one day, and strong the next...it's pretty random. So, It wouldn't even have to be a decrease in flow at night, perhaps maybe even a periodical increase in flow, and maybe not always at night, but on a more random schedule...

What benefits would one see from this? I don't know really...but I doubt it would hurt anything. I however would think that if you have good, random flow in your tank already, trying to vary those flow rates would likely be more of a PITA than anything. If some good evidence comes up that suggests varying flow rates helps corals, I'll rethink my postition...

MikeS