Reduced flow at night -- good idea?

[geno]

Gonna try to use the RND and OSC function in my ACJr and see what I get.

Now and then the K's make a brief noise upon starting up -- but for me it's not an issue. I'm more interested in creating a little side-to-side movement rather than a linear flow.

We'll see -- anyone using their ACJr to create random movement?

 

[geno]

Suppose I buy a wavemaker and plug them in? I think I'll have the same problem since I think most wavemakers (at least the ones I'm interested in) only slow the pump -- no turn it off. There in lies the problem with the original Koralia's -- slowing down the motor is not considered a good thing.

I just hate spending $300 to $400 for a new set up.

 

[acroholic]

Xyzpdq0121;313265 wrote: Most newer research suggests that your skimmer does not really impart too much O2 into the water. Not enough to make up for poor surface agitation and flow.

Loren,
Have you got a reference for that research. I would be interested in reading it. Thanks.
Dave

 

[geno]

Dawgdude -- you are correct -- I still don't like it -- but you are right.

I guess I'll just leave things as they are -- frankly everything seems to be working well now -- messing with it will likely screw something up and I'll get angry with myself.

 

[xyzpdq0121]

Acroholic;313576 wrote: Loren,
Have you got a reference for that research. I would be interested in reading it. Thanks.
Dave

First off, it is Brandon, not Loren... He is not this smart! And, I am my own references!!! J/K

Sure... I know Tom Wyatt has done a lot on the subject and I have talked to him in depth about it when I was helping design a simmer for someone. I am not sure if Tom has "published" anything on the topic. You might want to google Tom Wyatt and "simmer O2 levels". I know he posts over at TRT (the reef tank) and I think he made some posts on the subject about a year ago, you might want to search over there. His screen name is tdwyatt, I think. I know a write up was done for a class taught by open learn. You can find the O2 section http://openlearn.open.ac.uk/mod/resource/view.php?id=185880">here</a>. A lot of what has been researched for the past 5 years or so comes from waste water treatment plants. (For those of you that do not know, that is where we get the skimmer technology better known as foam fractionation.) Millero has a GREAT book out there called "Chemical Oceanography" I believe. But like Noga's book on fish pathology, Millero's book is way too expensive for anyone to own and read (about $100). But if you can get your hands on it, it is very good reading for chemistry and physics nerds.

Long and short of all of it is that O2 and CO2 are in equilibrium with each other, in and out of the tank. Lets say you injected pure O2 into your tank. Since the O2 level from the outside air that your skimmer is pulling is not pure O2, you skimmer will actually pull more CO2 out of the air to maintain the balance, thus reducing the O2 levels in your tank. So in this extreme example, a skimmer is harming your O2 levels. On the other end, yes a skimmer will add O2 to your tank only if your tank is producing more CO2 then is in saturation in the outside air. Other then that, it does not add any additional O2 to your tank. And your tank can only hold so much dissolved gases so the saturation level is set, the mixture is the only thing that can change. Now what that said, if you have a large area of CO2 (say in your main tank) and you are trying to balance out the gas levels using a skimmer in your sump, you run into two problems: 1) Your skimmer can only equalize what is in the body at the time and 2) it will be limited at the rate of your return pump for "resupplying" the O2 balanced water to the display tank. (Granted this is hypothetically in a vacuum since surface area will assist the display tank in gas exchange.) So if the rate of your CO2 production at night exceeds the rate of balanced gas exchange done by your skimmer + the rate of your return pump.... Then your fish suffer from lack of O2 levels and sooner or later death. To add one more layer to this problem, the more "contact time" your skimmer has with the water (while in chamber) the worse your skimmer helps to maintain the balance to the rest of the tank, since it is not as high of a turn over. So in this regards, a good skimmer is actually worse for O2 stabilization then a crappy skimmer is! The reason this is not a problem during the day is because corals and micro-algae are photosynthetic and convert CO2 to O2 with light. Your lights are on during the day and so problem solved.

 

[xyzpdq0121]

Oh, I forgot to add... Factors that go into the absorption rate of O2 into salt water are the levels of salt in the water, demand for the O2 (as mentioned above in the CO2:O2 ratios), the atmospheric pressure on the water, the temperature, the amount of junk in the water (organics, chemicals, etc), the surface area and the rate of the water flow (turbulence). You would figure that a skimmer gives one of these criteria easily, turbulence. But what it is lacking is surface area to volume ratio. Skimmers are not made to dissolve O2, if they did they would be pretty bad skimmers because you need bubbles to produce foam and thus skimmate. Bubbles break at the surface, not in the skimmer body. So if you could design a very wide, shallow skimmer you might have some hope of imparting more O2 into the water, but it would make for a very poor skimmer.

It is possible to supersaturate (more O2 in the water then is in the outside air) the water with O2. This is what happens during the day when your corals and algae are producing O2. This only happens in the day time, with a healthy tank and only happens because the surface area of the tank and what is being drawn out by the skimmer (see above about the skimmer importing CO2 into the water) is not happening as fast as the corals and algae are producing O2. Luck in this case, just like your skimmer is not built to put O2 into the water, the exchange of putting CO2 into the water is not very efficient in a good skimmer. But for proof that it does happen, all you need to look at is the people who move their air intake for their skimmer outdoors in the winter time to help not pull so much CO2 from a cooped up house. But that is a small fix in the overall design and chemistry/physics problem in how it all works.

Ok that is all for tonight, my brain hurts!

 

[ralph atl]

Bottom line is that corals respirate with flow. No flow; no O2. A real reef will have less waves at night due to atmosphereic conditions, but you still have major currents that cannot even begun to be replicated in a tank.

The area surrounding a coral must be broken, or it will suffocate. As Loren states, a skimmer is minimal at best. The water surface and the minute area surounding a coral is the best way to insure gasses are being exchanged.

 

[xyzpdq0121]

mysterybox;313780 wrote: No flow; no O2.

First off, No O2 would be a good thing since O2 is of no value to a coral anyways.

Ummm. I do not get this Ralph. Corals do not "respirate" at night. (They do not respirate at all but now I am parsing words! ) I could see your point if you were talking about the daytime when they need CO2, for the carbon, and expel O2. Without water movement, I could get the argument that the water around them would become supersaturated with O2 and thus they would run out of CO2 to convert. But this theory is just taking some major leaps in physics that does not really happen. What would be more likely the case is that the O2 being produced would cause some "flow" of gases in the water. I mean, that is like saying if I put you in a room with no air flow and you could not move, the air around your head would become so riddled with CO2 that you would die, even if there was plenty of O2 at your feet. Or, in a forest if there is no wind movement, all the plants die! Just does not work that way.

 

[ralph atl]

Yeah, I was using respirate very loosly! They do need to exchange gas, food, and expel, though. Also, there is a water tension that surrounds a coral, although I am not using the correct term as I'm on my phone. Polyps need to exchange food at night, too!

 

[xyzpdq0121]

Well starvation is different then gas dynamics and even that is debunked pretty easy with a theory that you should have plenty of organic matter in the water to feed the corals anyways. Plus a pod crawling across the coral would break your water tension.

But that is enough from me because it is bed time!

 

[ralph atl]

This is what I'm talking about. Corals need flow or you wouldn't need powerheads at all. They are sessile animals that need water movement to exchange gases, food, waste, and elements in order to survive. At night, the polyps are even more important as they are the only means as the algae is not active.

This is even more so important in low nutient systems that breed bacteria to lower levels of phosphate & nitrates. This bacteria slime can also coat the corals which proper flow will remove.

In the wild, reefs have currents 24-7, even at night when the surface is more calm due to weather. Underneith, the currents bring life to the corals. Can they deal with less current at night? Sure, but it still must be sufficient. Can they deal with less current during the day? Sure! Less light? Sure? Less calcium? Sure? But there is a point where you've reached the line.

mysterybox;312762 wrote: Because when the lights go out there is heavy respiration by all the animals and plants in the tank, but there is no photosynthesis to replenish the oxygen consumed. Oxygen levels, even in nature, drop dramatically and the water near the reef surface becomes hypoxic at night. Water motion helps to bring in oxygenated water and is especially important for animals like corals that rely on diffusion of O2 from the water column. There's actually a thin layer of water that "sticks" to the surface of the corals and becomes especially low in O2 as compared to the overlying water. This boundary layer forms a barrier to diffusion of O2 in and CO2 out of the coral, essentially suffocating it. The faster the water flow, the thinner the boundary layer. It doesn't make sense to increase the boundary layer when O2 is already at it's most limiting.

Essentially none of our animals actually sleep and those that enter some state or torpor don't need lower flow to do so.


Also, many corals extend polyps to feed when light is lower, meaning they would prefer motion to sweep away waste and also get fresh nutrition, near as I can tell. Good question though - great, in fact, since many wavemakers offer a nighttime mode to stop the rocking and rolling.

Also, just because the surface waves may calm down, doesn't mean the currents below the surface have altered by much

 

[xyzpdq0121]

See Ralph, the problem with your quote is that it is not your original thought. Internet plagiarism is a growing problem, be part of the solution. I can copy and paste things from "greenbean36191" and "ocean size" and "billsreef" too. It is copied and pasted from reef central and takes some major leaps in marine biology and chemistry that are impossible to prove but contains some major flaws. Like, how important is O2 to a coral?!? We know that corals need some O2, since they are not strictly plants, they are animals and MOST animals need O2 (not all). There is a school of thought that says that since there is no O2 production from the zoo at night, O2 "respiration" at this time is more important. I can get that and buy into that theory but how much we talking here?!? The original poster was not talking about running his tank stagnate all night. I agree, this would be bad on a couple of levels. But a moderate slowing down of water should/would not hurt anything. Heck, you could make the argument that since this is when many corals put out their feeder, slowing down the water would allow for more contact time with food particles and thus greater feeding success rate. It is the difference in trying to catch a Nomar fastball over one thrown by your dainty butt.

 

[geno]

Thank you for restating my original request for advice; i.e. would reduced water flow at night be a problem -- NOT -- would shutting down all PHs be wise -- even the novice that I am knows better than that.

As it turns out, I have returned to my normal operation of running all PHs 24/7. I didn't like the clatter I got from my K's when I had them cycling -- frankly upon restart my fish didn't seem to like the noise either. They got startled and bolted to the other end of the tank. I figure why introduce noise stress to my healthy fish.

I certainly have learned a lot from this thread and appreciate all the content -- even if some of it was over my head at present.

Regards,
-gene

 

[xyzpdq0121]

Thanks for the topic Geno... It helps keep me on my toes. I have enjoyed revisiting the topic. (and giving Ralph a hard time)

 

[ralph atl]

Brandon, I guess we will have to agree to disagree..... and those quotes are exactly how I feel about the situation, they just worded it for me quicker. I wasn't quoting for "verifiable marine biologist references".

On an additional note to this topic, I have also found personally, that when I used the night mode on my controlled 2 Tunze 6000s (at least 6 months), my corals did worst & I had more algae & cyno issues. I think my pipefish loved it!



anyway, isn't there a tradition that EX PRESIDENTS REMAIN SILENT! LOL!

 

[ralph atl]

OK, here is an awesome article that dismisses Brandon's anaology that water is like air! I mean air flow is always happening unless you are in a airtight container? Let's TALK ABOUT FLOW!

Flow is more important than light:

 

[xyzpdq0121]

No we do not have to agree to disagree... we have to agree that you do not understand what you are spewing from your mouth. (or fingers as the case might be) This is kind of like the time you tried to convince me that Randy Holmes had written articles on fish pathology. Do you not realize that I (along with people like Jeremy, Raj, Steve, Kevin etc) know most of these people that you quote from personally? We have these conversations over drinks at MACNAs and dive trips.

You are right, Jake knows his flow dynamics better then I could ever hope to. I have talked to him in length about it. I do not agree that flow is MORE important then light. But I NEVER said that there was not some sort of diffusion boundary layer in flow dynamics, heck there is in everything according to molecular physics.

See your problem is that you keep on switching topics. First it is about O2, then it was about food and feeding, now it is back to O2. As I stated earlier, flow dynamics is very different then source feeding done by corals. You keep on mixing the two. For feeding of particle matter (phyto, micro food, heck even macro foods), slower flow would dictate a higher success rate of food capture. As a current ebbs and flows in the ocean, you have a period of high velocity and a period of calm. Theories (and much fact in research) shows that a coral captures most of its food during the moment of ebb. The flow replaces the food captured in the ebb with new source food. The cycle begins again. Now in many corals, they leave their feeders out all night. Once it has captured all the food it can, the feeds can not capture any more. So it would not matter if you had a tank of nothing but phyto. Once it is filled up, it is done for the night. So for feeding, it would not matter if you had slow flow and an ebb or fast flow and an ebb as long as you have the ebb to allow the coral to have contact time with the food source. Now, most tanks do not have an ebb and flow system in place. The flow is either 100% or it is off. So if you blast your corals with lets say 1000 GPH water all the time vs having flow of 100 gph, you can expect the coral to not be able to feed as well because it can not capture food as easily. Which moves us into out next topic, O2 exchange.

You are correct, via Jake's article. that physics dictates that you have a smaller membrane at higher flow rates. I said prior that one of the properties of gas exchange was velocity of the water. So you just found out that Jake says the same thing. But what I wrote was about why a skimmer does not impart O2 into the water like most people think. As far as my comment about air vs water... Water flow is happening even in a sealed system with not pumps. On the atomic level there is always an equilibrium trying to be reached, this causes water movement. Much in the same way as high and low pressure systems cause wind. You did not think that that cool breeze you felt on a summer afternoon was caused by a guy in Texas with a really big fan, did you?!? So even in the small membrane layer in Jake's description, there is gas exchange. Now with more O2, due to the faster flowing water on the outside of the membrane, there is more gas exchange happening (see post above about 02 and CO2 reaching a balance in ANYTHING). But how much lack of flow is needed before you "suffocate" at coral. Most would contend that this would not happen in a normal aquarium trying to reach an ebb and flow system. Sure, you leave your tank stagnate for a day or two and you might come close but that is not what the OP was going to do. But what would it take?!? I don't know. Most research on the subject has been done in reference to sediment "suffocation" in corals. We know that Porites, for example needs so much oxygen (in the case of this coral it is 0.010.+-.0.001ml O2 cm'-2' h'-1'). We also know about how much it can uptake under normal conditions. What we do not know is how much O2 and CO2 are in YOUR tank! But even not knowing how much O2 is specifically in your tank, I can tell you, baring anything like sand clouds or calcification "snow" you will not reach the levels of "suffocation" that you speak of.

So, yes, Jake's writings are very good. He is great with flow dynamics and his work on turbulent flow (known as the "Jake effect") vs laminar flow is really good. He really knows how to achieve the Jake effect in a tank and I agree, it is really useful. But, again, please stop taking parts of articles and other people's comments and piecing them together without understanding what you are trying to argue or the bigger picture of how it all works.

Edit: BTW, I am not getting pissy, I mean all the stabs in jest.

 

[ralph atl]

dawgdude;314037 wrote: Oh jeez lets just not bring up Phosphates! There are many tanks out that that are at less turnover than he would even be running at night with the main PHs off but for some reason people are crying that corals will die. Funny, I have a 29g with a MJ 600 return only and all my corals are fine. I think some people tend to exaggerate a bit....



Well when the EX President is more knowledgeable than 95% of the club on the subject then who else will be there to call people out and correct them?

Charlie, PLEASE ignore my posts as was previously discussed by ARC. I made a joke to Brandon (with an LOL), and he is smart enough to "get it".

......and yes, he is smarter than the 95% of the club, just not the 5% that I'm in. LOL!

 

[xyzpdq0121]

Ok you two, lets keep this good clean fun. Charlie, thanks for having my back but Ralph is no challange. I got him on lock down. When he comes up with an original thought or artical on the subject, then I will be worried... until then he is no match for me!

Now time to use my handy Iphone to call Jake's wimpy phone and tell him how much of a shmuck he is!

 

[ralph atl]

Brandon, I just don't see where you are adding anything sound, you are just trying to discredit my posts. Bringing up an error I made 6 months ago (which I had previously explained that I was at work, on a phone, without reference quoting from memory.) This has nothing to do with flow. So, I will leave this thread on this great article again: