Does high flow really matter?

[Afterburner]

I hear a lot about needing less flow or current for some corals, but does it really matter much to have high flow. Seems like all the pump vendors show off these incredible flow tanks that look like the inside of a washing machine. I can tell you that I have SCUBA dived reefs all over the world, and never been in any high current situations. I know that having some flow is essential, but how much is really needed? I currently have a mixed reef tank for the past 5 years and I never had and incredible amount of flow in it. I forget to clean my gyre and it ends up hardly pumping at all, yet the corals seem to grow fine with good polyp extension, so does high flow really matter?

 

[kad1979]

I will be curious to watch this thread. I dive too, while I agree most reefs are not high flow like you see in some as you describe washing machine tanks but you've got to think about the amount of nutrients and goodies in the ocean vs. what we try to replicate.

I once did a drift drive in Bali....we were moving!! Weeeeeeeeee.....

 

[fish farmer]

Have you been on those reefs during a storm event? That's when they really get pounded.

It's all relative to what coral you have, how much stuff settles on the rocks, etc. How much you want stuff in your tank suspended and removed by sump filtration.

 

[Afterburner]

I didn’t think about the detritus, but there are always eddies where it will build up anyway. I usually just take a turkey baster to the tank once in a while and stir it up anyway. I have not had a high flow environment for a long time and it has not been detrimental to either my SPS or LPS from what I can tell, but I don’t have another tank to compare it to.

 

[SlugSnorter]

I hear a lot about needing less flow or current for some corals, but does it really matter much to have high flow. Seems like all the pump vendors show off these incredible flow tanks that look like the inside of a washing machine. I can tell you that I have SCUBA dived reefs all over the world, and never been in any high current situations. I know that having some flow is essential, but how much is really needed? I currently have a mixed reef tank for the past 5 years and I never had and incredible amount of flow in it. I forget to clean my gyre and it ends up hardly pumping at all, yet the corals seem to grow fine with good polyp extension, so does high flow really matter?

depends on the reef. Some need it. Most dont

 

[BanjoBandito]

I've always had better extension and propagation with higher flow. My zoas will spread quickly, torches extend better, and any SPS I try and blast it. You can over do it though. Flow is a pretty subjective topic.

 

[RSnodgrass]

I'd think of it differently...
In your aquarium there are numerous factors that lead to optimum coral health. If one of those factors is off (low) it does not necessarily spell doom but rather the other factors need to be on point.

Also having dove around the world, keep in mind the guides tend to avoid taking us where the current is. If you want to see alot going on dive where the current shows up during a tide movement. Different animals, coral tends to open up, etc.

All that said it's never ripping all the time for most coral areas I've seen.

Either way a simple test is alk consumption rates over a couple of weeks would answer it.

 

[Afterburner]

I have only been on a few guided dives. I do a lot of diving off my own boat without really checkging for current. Sometimes the current is a bit strong for diving with full gear, but the only places I have seen extreme currents similar to what people replicate in thier tanks is under bridges in the keys. I have not noticed any better looking coral where it rips vs. offshore reefs that have much milder conditions most of the time. Someone mentioned it depends on the reef/tank. Hopefully they can provide a bit more value to that statement with specifically what needs the crazy currents.

 

[dvgyfresh]

Very subjective, sps tank would appreciate high flow, I have highish flow in my DT. Helps keeping no dead spots , allows all organisms to receive food because water is always moving, no surface protein build up, water is clearer,

 

[mdb_talon]

Personally i think very high flow can be great for a lot of sps and i do notice a difference based off flow. Of course though it drastically depends on the coral. If i put a hammer in my acro tank it would likely be dead in a couple days. When you have a mixed tank then of course you have to find a good balance and hopefully have higher and lower flow spots depending on the corals in that spot.

 

[damsels are not mean]

Flow is tough in a tank because it's an enclosed space with little directional pumps. In the ocean, flow is really higher than most tanks (ok depends on where and when to be fair) BUT it is spread out and multidirectional. It is hard to match this high flow in our tanks without ripping the flesh off of corals because balancing spread & turbulence with strength is very difficult.

 

[Afterburner]

Even in the worst case conditions in a real ocean reef, high flow is only for short durations around a lunar cycle. What I am seeing in some tanks is way over that amount and even though it is changing, it is usually throughout the day, every day. I used to think it was important also, but when I gave up on it I did not notice much difference except maybe slower growth. I am weird and prefer less growth because it is less work for me having to prune corals that grow into others. I have noticed my hammers are really growing fast and big though. I am starting to stack corals in the water column now, and my idea was to have some floating in the middle of my tank, so too much flow would be a problem for that (there is a thread with a pic of what I am talking about i on here https://www.reef2reef.com/posts/9889384/) I will attach a pic when I clean my glass and get one.

 

[MillennialReefer]

I have a Tunze 6040 that's responsible for 95 percent of the flow. I think the most difficult part of flow is creating one large 'current' and that's where the wave setting comes on, since its not a concentrated unidirectional high flow but rather moving all the water at once - if that makes sense. I didn't have it in the system the first month it was set up, however since installing it I've noticed more fish activity (not just lingering in one spot) and polyp extension.

 

[Afterburner]

Here is a video of the floating corals. I just put the pocillapora in there and will probably have to secure it in one place so It won't move around quite so much. There is another floater that is anchored to the bottom by a fishing line in the view. As you can see, there is very little current in my tank and everything seems fine.

Floating corals suspended from top and another from bottom

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[bruno3047]

I hear a lot about needing less flow or current for some corals, but does it really matter much to have high flow. Seems like all the pump vendors show off these incredible flow tanks that look like the inside of a washing machine. I can tell you that I have SCUBA dived reefs all over the world, and never been in any high current situations. I know that having some flow is essential, but how much is really needed? I currently have a mixed reef tank for the past 5 years and I never had and incredible amount of flow in it. I forget to clean my gyre and it ends up hardly pumping at all, yet the corals seem to grow fine with good polyp extension, so does high flow really matter?

I think the high flow is important for SPS mainly. Most of the LPS that I either have or have an interest in require low to moderate flow.

 

[Afterburner]

I think the high flow is important for SPS mainly. Most of the LPS that I either have or have an interest in require low to moderate flow.

Check out the video, I have plenty of SPS doing fine with almost no flow. I have read about people growing corals in glass jars with no current or even bubbles and they seem to do fine, so why do people think you need massive flow? I'm not saying I am going to turn off my pumps, quite the contrary, just keep it real. The floating experiment was to get my SPS to move around in the moderate flow like LPS do.

 

[bruno3047]

Check out the video, I have plenty of SPS doing fine with almost no flow. I have read about people growing corals in glass jars with no current or even bubbles and they seem to do fine, so why do people think you need massive flow? I'm not saying I am going to turn off my pumps, quite the contrary, just keep it real. The floating experiment was to get my SPS to move around in the moderate flow like LPS do.

Because if you go and look at any SPS Coral for sale anywhere, in the “care” section, they always say “high flow”. I agree with you. I think a lot of this information coming out of the retailers is BS.

 

[DivingTheWorld]

I find in general, acros prefer high flow. In my 80g I run two MP40's at 90% Reefcrest Antisync 24/7. I'm at 100x not including my returns. I did experiment with even more flow and added a third. In a tank with a lot of acros, it's easy to tell quickly when they are happy or not. My Alk/Cal started increasing so happy they were not. 2 MP40s turned out to be my sweet spot.

It also depends on the acro. For instance, I find that millis love some of the highest flow, tenius somewhere in the middle, and there are some acros that do well in low flow (ex. Secale). But I can tell you that I have a few spots with very limited flow in my tank, simply due to rock structure and acros do not do well in those spots.

The only way you will know what works best for your tank and corals is through experimentation. Increase flow and see how your corals react. Decrease flow and see how your corals react. Move pumps around to make sure you have good indirect flow in the majority of areas.

IMO the average acro prefers high indirect flow (100x).

 

[HudsonReefer2.0]

@Afterburner you dive so you get to see the reef in its natural state. So u get it and replicate what you experience in the wild to the home reef. Glad u can replicate this and understand the amount that works for your system in relation to gas exchange and nutrient export I run 2 Nero 5 on the back of my xl300 and people commemt that’s all u have for flow. I’m like yeah. It’s like 5k ( not 100%. )an hour on pulse moving 21”. What about the sides. I’m like what about them. This works for my system. Mixed w a good amount of sps.

 

[MaxTremors]

There’s a lot to unpack here. First the flow that we get from pumps is nothing like the ‘flow’ in the ocean. In the ocean, corals are seeing much more water moving past/through them than even the highest flow tanks. So, while to your eyes it may look like they’re not getting much flow, in reality they are getting orders of magnitude more flow than in our tanks. The other thing to consider is that the ‘flow’ in the ocean is not as directional and laminar as it is in our tanks, there is multidirectional, turbulent, rolling ‘flow’ on natural reefs, so again, to our eyes it may not look like as much flow because it’s not all going in one or two directions. And then on top of the regular multidirectional turbulent flow, there are ocean currents, the tide, upwellings, storms, etc that add to, change, and influence the amount and type of flow corals receive. It’s nearly impossible to replicate in a small, closed box. Even big surge machines used by public aquariums and some larger private tanks don’t come close to matching the amount and type of flow corals see in the wild. The type of flow we can replicate in our tanks is not ideal, the only way we can move enough water over our corals is with pumps that by their very nature, are unable to provide the amount and the kind of flow that corals experience in the wild.

To address the question of whether or not corals need high flow. It obviously varies depending on species, and corals are quite adaptable, but the answer is ‘yes’, they do need high amounts of flow. To properly respirate, corals need quite a bit of flow. Flow also dictates the amount of photosynthesis that can be achieved, pulsing Xenia has the highest rate of respiration and therefore photosynthesis of any known coral, because it pulsing action effectively moves water into and then away from the colony. High flow is also important for moving the byproducts (free radicals) of photosynthesis away from the coral, without adequate flow moving these free radicals away from the coral, they experience oxidative stress that can breakdown proteins and cell membranes and ultimately even kill the coral.

Lastly, high flow is important for keeping detritus suspended so that it can be filtered out, it can be a deterrent for nuisance algae/Cyanobacteria to grow, and it ensures proper oxygenation for all of the aerobic life that lives in your tank. High flow is also important for fish, many fish need high flow to stay fit and healthy. Active fish like and need high flow to swim against, fish from tanks with low flow can be become obese (over feeding is also part of this, but lack of flow is undoubtedly part of the cause in many cases - and like with humans in North America, obesity is far too common in captive reef fish). It can also be considered enrichment, I know my fish seem to enjoy swimming against the flow.

Overall, this just seems like a really bizarre thing to be questioning, as it is, for all intents and purposes, settled science. As I said above, corals are highly adaptable, and so long as they’re getting enough flow to respirate and photosynthesize, they’ll survive, but to truly thrive, they need a good amount of flow (again, what constitutes a ‘good amount’ varies depending on species).