Flow Rate In A Reef Tank.

[1234-fishy-freind]

Hi there.
I was just wondering if someone could give me a rough estimate as to how much water flow a reef tank with corals in should have in either
-gallons per hour
or
-litres per hour
depending on the size of the tank.

thanks

 

[rabbut]

You want a turn over of at least 20 times an hour for "easy" corals. Some like more, others less. My Organ Pipe is only happy directly in the outflow of one of my 2500lph pumps, buy my Bubble Coral would just disintegrate with that flow. As a rule you want between 20 and 30 times an hour though

 

[ben1987]

depends what type of reef?
Lower flow for softies and LPs 20X ish
Sps needs to be way up. Minimum of 30X

 

[1234-fishy-freind]

Well its a mixed reef with differnt sorts of corals mainly softs and lps. So i think somewhere around 20 will do.


thanks guys

 

[SkiFletch]

I'd aim for 20-30 with that general coral description

 

[Crazy fishes]

Flow rates are really difficult to get right. Ben says 20x for LPS and my LPS couldn't stand that. At the moment I have little over 10x and one of my hammer frags is finding that hard yet another frag of hammer behind it is fine. It depends on the tank size and shape as well as where the corals are placed relative to flow. It is a trial and error process largely. How big is the tank? As a rule the bigger the tank the more inertia the water has and therefore go with the upper limits of the 'suggested' flow rates e.g. 24g LPS tank is a small tank with deep water corals therefore flow should be about 10-15x however in the same tank with SPS corals you are aiming at 20-30x. The interesting bit is that 20-30x in a 50-100g would be not enough flow for SPS and you start talking 40-50x. There is some really interesting read out there if you are interested.
One of the really intriguing points is that in the ocean corals are hit by alternating currents and this is very different from the continous mono-directional flow in our aquaria. It has been seen that the face of the coral receiving the flow normally is sujected to a more laminar profile. The flow pattern changes as a result of the interaction with the 'front face' and becomes more disturbed-turbulent flow which is what is transmitted to the 'back face'. Back to the ocean..... Alternating current means both sides of the coral experience being the lagging or back face as well as the leading or front face however in our tanks with powerheads and the like one face is always sujected to laminar flow and one to disturbed-turbulent flow. It should be said that corals prefer turbulent flow as it washes away debris and carries food particles to them but does not put a continuous strain on the polyp.
We should really place our corals behind objects so the flow is turbulent be the time it reaches them.
Then comes in those curious corals like my GSP and Rabbut's pipe organ coral that thrive in a mono directional flow that is blasting the polyps...... It does get a little confusing but trial and error is the key!!

Hope this helps

Regards

 

[ben1987]

Yeah some of my LPS like it in near on dead spots. They dont come out at all in real flow

 

[SkiFletch]

Careful... LPS extension does not necessarily mean the coral is "happy." Often times if flow and/or lighting is too low the LPS will puff up its flesh to increase surface area for increased respiration and photosynthesis... It really is a careful balance

 

[Crazy fishes]

If a coral isn't extending that much that is a worying sign and similarly if it starts to puff up like you say Ski that always sends shivers down my spine. If the polyp is out in the 'non-puffed' state then that is usually a positive. LPS when they puff up normally have a gaping oral disc as well which again in the absence of food is a little unnerving. We have all been there with prize corals that puff their tissue, have short tentacles and gape their oral disc; the normal response is to run around like a headless chicken because we feel (and have) absolutely no control over the possible demise . My Catalaphyllia will puff every morning in response to brine shrimp entering the water as does the Fungia Spp now I think about it. It seems we have no definite rules only general guidance. The complexity of these corals eh Ski.... Why would a coral puff it's tissue under these inadequate conditions; by puffing it decreases its surface area:volume ratio but it must have a purpose???

Regards

 

[SkiFletch]

Well CF, this is purely speculation on my part but while puffing up does decrease the ratio of surface area to volume, it would seem to me that the coral really doesn't care about it's volume. Likely the coral just lightly alters its osmoregulation and allows water into it's tissue. The resulting increased surface area (regardless of volume) means more gas exchange, more likelihood of catching food, and more ability to catch light rays. The increased water volume probably means little to the coral. Just thinking out loud

 

[Crazy fishes]

Echoing thoughts back.... gas exchange is dependent on surface area to volume ratio (the reason for people with emphysema are blue or breathing really hard, gas exchange is the same across all life forms) and as for catching more food the polyps tentacles usually retract slightly when they puff which would mean less chance catching food. It is an interesting issue to ponder........( CF takes five minutes to ponder ). A task for someone to take up; see if they is any research into LPS swelling in adverse conditions and feeding behaviour.

Regards