Jon Simmons

Today I came home to find that my powerheads were all turned off. (Turned them off this morning, forgot to turn them back on)

Before I noticed the powerheads I noticed that everything looked wonderfull. All LPS were expanded much more then usual, mushrooms expanded huge, etc... When I turned them on again the current caused the corals to shring again. (Light current on the SPS)

I am wondering aobut the possibility of running the powerheads only when the lights are off, at night.

Is this common? Is it recomended? The corals seem so much happier when the current is off.

Dallas Warren

That is assuming that a coral expanded equates to a "happier" coral. It really isn't quite as simple as that, there are a lot of factors involved, in particular with how much a coral will expand. Some of those are

• amount of current. The tissue can only take so much shear, and beyond that it will tear. So the coral has to keep the tissue to such a size/distance/exposure such that it wont cause any damage
• amount of light. The larger the surface area of the coral, the more light it can collect, and therefore the more energy it can gain from its zooxanthellae. Remember too that if it has too much light then it wont expand as much, as it doesn't have to
• if it is feeding or not. The feeding tentacles have to be placed such that are out in the current to capture prey as it floats past

An obvious example of an expanded coral that isn't happy is mushroom anemones when they extend up in a trumpet like fashion towards the light. They are trying to extend up into more light, as what they are currently getting is insufficient.

Remember that using one indicator of whether something is doing well can be a bad idea. Some things occur for more than one reason.

As to whether to do it, well provide enough current so that the coral can't expand out fully, but doesn't withdraw into the skeleton completely. Sort of a happy medium between the two extremes. This gives you quite a lot of leeway as well, and periods of surges and calm is the way to go (more natural for many reef zones).

Larry Robison

Anthropopathism- assigning or attributing human emotions to nonhuman beings, things etc.

It may be that they are not so much happy as trying to get the greatest surface area exposed to the water, to respire, as the usual gas exchange system is not operation.

Mike Kirda

One thing that I have to mention- at no time during any of my dives did I notice an abundance of LPS- there are just not many to begin with, and to top it off, in my entire time in Tukang Besi, I don't recall seeing a single LPS coral...

Where I did see them was in the Philippines, in Batangas, in an area called Twin Rocks and Sepok Point. Much more in Sepok Point, but remember, this is based on my limited observations of the area, not any transect or quadrant data.

As I rounded Sepok Point, I was at about 45 feet of depth. Sepok is a wall, really. What struck me about this is that the divemaster, Mark, was nearer to the wall, maybe 10 feet away from it, while I was closer to forty feet away. Even at the depth of 45 feet, the surge coming in was impressive. If I tried to stay still in the water column, I was moving back and forth relative to the wall about 5 feet, due to the surge. Mark, on the other hand, was moving back and forth closer to thirty feet, again while trying to stay still.

Meanwhile, on the surface, one of the nearby dive sites, called Sombrero Island (looks like a sombrero, with a wide fringing reef as a rim...), was getting hammered from the ocean swell. Waves were cresting and breaking on the reef at about six feet- the sound of the waves could be heard easily 1/2 km. away.

This was the first time I have seen such a flow, and it really made an impression. The flow around the point was really incredible, and there was literally no way you could get close to the wall for fear that you'd get tangled in the myriad of corals growing there. You'd literally tear yourself to shreds.

That being said, I also think that there exists a boundary layer at some point closer to the surface of the wall. Within that layer, the current was obviously not that high-the fact that so many corals were sticking out, and that the surface was not at all smooth, would ensure this. The mixing was evident and still rather strong, but this area is one where I noticed the most LPS, in particular, Hammer coral. Not particularly highly inflated Hammer Coral, but it was not completely sucked in either.

Personally, if I was to anthropomorphize your coral, I'd say that it expanded to that amount to maximize the surface area in order to permit better gas exchange. Without movement in the tank that would normally allow this to happen readily, 'puffing up' would probably be the next best thing... And, while attractive, it does not particularly strike me as being a 'good thing'... It would seem to be much more of a stressor, IMO.

Jon Simmons

Thanks for everyone's input, I guess I will stick with my normal schedule of powerhead on/off times.

Bev Wladyka

On/off sounds like a black and white to a shades-of-grey problem. If this was my reef, I'd experiment with reducing water flow from the powerheads, placing PH in higher or lower positions, and make sure water flow does not directly hit any corals.

Powerheads move the water which helps it stay oxygenated. If left without O2 for too long, your corals and other animals will certainly suffocate o(