Velocity in the Aquarium

[Maivortex]

I was hoping to find out if anyone has info regarding the velocity (cm/second) that is intended when we speak about low flow/ med flow/ high flow corals. For example, I have not seen any discussion about low flow= 10 cm/s, high flow= 30 cm/s. Perhaps this data has been taken in the ocean? Dana Riddle wrote this article about velocities of different Tunze pumps:
http://www.advancedaquarist.com/2013/4/review
But this article does not specify what would be observed in the ocean. Does anyone know of any more articles about flow in the a natural reef. Dana Riddle may have written about this but I can not find it, a long time ago, I helped him collect the data so I know the data does exist.

I have an opportunity to map flow rates in my aquarium vertically and horizontally using fluent ansys equipment. This data would be very useful if I knew the velocity specific corals require.

 

[Bilk]

Subscribed. Interested to find out more about this.

 

[Boston21]

I don't think many people are this scientific with fluid dynamic's in reef's but it would be great to know. Tagging along!

 

[synapse2]

tagging along

 

[Joe0813]

following just because of your picture

 

[scolley]

following just because of your picture

+1! :thumbsup: But the OP is asking a great question...

I suspect such information is not readily available is because there is little most hobbyists could do with it if they had it. We agonize over our PAR, in part because it's something we can easily measure. But flow? With no easily accessible way to measure it, it receives too little attention.

Subscribed.

 

[r-balljunkie]

This data would be very useful if I knew the velocity specific corals require.

I dont think you can quantify a certain flow verses corals needs unless you knew exactly where it was collected.

some species are found in lagoon, where you never see a current, and its relatively calm around 60'+.

some species are on the open reef near a pass, where you getting a ripping current when the tides change.

some species live right on the break, pounded day in and day out by the surf.

corals are very resilient species. i'm always amazed where they show up on the reef.

you might have better luck trying to find out where a species you are interested in comes from (lagoon or open reef) and attempt to provide flow needs that closer to where they are found.

good luck

C

 

[SGT_York]

+1 to above and add that the currents are not stable but always change, at least twice a day with the tide and even more with storms and seasonal changes. Considering the corals come from hurricaine areas they are very resilient to flow changes.

 

[Pastey]

There are a number of things we can't really replicate in our tanks. While we might be able to meet a certain velocity of a certain area in the ocean, velocity is really only part of the equation. The importance of flow for corals is to constantly be supplying nutrients. In our tiny tanks, we can never really hope to match the volume of available nutrients without potential issues because our nutrient export. When I was planning my current tank, flow was a huge deal for me. I wanted lots of it but I didn't necessarily want a ton of VOLUME. I opted for multiple, smaller power heads that can interact with each other to create chaotic flow. I wanted non-laminar (turbulence). This is something you can't really measure for..well..I'm sure you can but for our intents and purposes, it's probably not worthwhile.

 

[dkeller_nc]

Perhaps this data has been taken in the ocean? Dana Riddle wrote this article about velocities of different Tunze pumps:
http://www.advancedaquarist.com/2013/4/review
But this article does not specify what would be observed in the ocean.

Huh? Yes it does - there's a table in the first of the article that's reproduced from one of the references that specifies water velocity ranges for different parts of the reef. While it isn't species specific, one could easily infer at least genus-specific information. For example, it's a pretty safe assumption that Acropora, Porites, and other SPS corals will be predominate on the reef crest, while LPS corals would predominate on the back reef or lagoon areas.

 

[Timfish]

. . . . While it isn't species specific, one could easily infer at least genus-specific information. For example, it's a pretty safe assumption that Acropora, Porites, and other SPS corals will be predominate on the reef crest, while LPS corals would predominate on the back reef or lagoon areas.

I'm inclined to see this as an inaccurate over generalization. Looking at Veron's "Corals of the World" just with the Acropora genus there are species found in mutually exclusive habitats. Some are found in turbid and or protected lagoons(A. tortusa) while others are found only on reef crests exposed to wave action and others just don't seem to care. Of the so called "LPS" the genus Alveopora, Gonipora and Oulastrea have species found only in shallow reef environmnts exposed to turbulence. Many of the species in Favites and a couple of Acantastrea and Lobophyllia robusta are quite cosmopolitan and are found in "Most reef environments". Fungia scutaria likes reef slopes with strong wave action while Euphyllia ancora likes shallow water with moderate wave action unlike most of the other species in the genus.

+1 to what Patsey said and I would add that while a species may be found with certain flow rates in the wild many of the aquacultured colonies we may get are arguably domesticated and quite likely would not survive "real" conditions (look what happened with the Stienhart aquarium in 2008). Mosts aquacultured corals we get are going to be relatively tolerent but it's always best to find out the conditions a colony was grown under and duplicate those conditions.

 

[dkeller_nc]

Well, yeah, it's a generalization. But it's a pretty good rule of thumb. And I can confirm from doing a lot of diving that there are some species that have a very large tolerance range and can be found at a lot of different depths and flow regimes. Nevertheless, the rule of thumb may be about as good as we're going to get. Heck, it's difficult to get even light intensity data on species available to the hobby - whether an acropora species is "deep water" or not, for example.

 

[N1ceDrgn]

you might have better luck trying to find out where a species you are interested in comes from (lagoon or open reef) and attempt to provide flow needs that closer to where they are found.

good luck

C

This is actually what I just finished doing in my own system. I've had a 125g up and running now for almost 7 years and only recently decided to change up my aquascape. I planned to use the LR I've had, I only changed the different rock structures and placements of my powerheads.
While I tried to redesign the aquascape, I also read up on the different SPS I have in my tank and then placed them according to what I found online and in the books I have on corals.
So far, most have responded well to this customization. I'm nearly finished with the entire system and once I am, I hope who I do have in my system will respond like some of the SPS already has.
While I don't have static numbers for how much flow and lighting in different places and levels within the aquarium. I have just been watching how long polyp extensions have become and the subtle color changes in the different corals.
It has been a lot of work to get this far but I am happy to share how nice things are turning out. The effort in really knowing what I have and where it's from, combined with what kind of environment I can recreate in my system has been a learning experience, both painful (time intensive) and rewarding (when I see how everything is responding).