Natural Variations on a Reef

[Soultwater]

I have over 300 scuba dives on the reefs of Okinawa Japan. Prior to this I considered myself a reef aquarist for over 8 years. In my scuba diving days, I have witnessed on many occasions water temp shift greater than 10 degrees within a few feet of water sometimes as much as 30 degrees. I have witnessed stony corals growing in 94 degree water on really hot days. I have witnessed huge rain falls that would cloud the reef with the changing salinity. Sometimes I wonder why everyone is complaining if they have a mild shift temp change during the day. Been reading that you should only add make up water a cretin or you will stress your animals. I think it would be better to not have such a dramatic change but some people are claiming this is what killed there gold plated dragonbreathing green and red rainbow colored extra spensive coral. I am thinking that not knowing how to care for the coral in the first place is most likely what killed it.
No but really what is the big deal any way? The Natural Variations on a Reef do occur or does everyone thing it’s a constant 70 - 75 degrees

[thegrun]

Very true, in nature corals see a lot of variations in their environment. However, the corals we keep are under a fair amount of stress due to the fact that we cannot fully mimic the conditions found on a reef. Due to that stress, the attempt to keep our water chemistry stable is a good idea, as one more thing out of line could be the straw that breaks the camel’s back. Do I worry about the 4 degree swings in my tank's temperature or small Ph swings during the night? No not really, but I would say that overall water stability is a key to long term success.

[lordofthereef]

I think it is all about optimum growth and such (or at least what we perceive it it be). Our critters have natural predators in the wold too. When we get one of these predators in our tanks we do all we can to get rid of it. Why? Because we don't want to adversely effect the creatures that we spend so much effort and money raising. I have often thought about temperature swings, and I know tropical areas get high heat mid day especially in the summer. Also tons of rain I am sure is a frequent occurrence. To some degree I think we have sold ourselves ib sine ridiculous concepts.

As a sidenote, when my tank hit 94 degrees last summer due to a malfunction none of my corals were happy LOL.

[jflick345]

Natural variations exist, yes, but as lord stated we strive for the optimum conditions to achieve the best results. Corals are tough critters, no doubt about it, so they will most likely survive certain stresses. (Like when I left a birdsnest and mushroom frag sitting out for a few hours. Oops.) People tend to blow things out of proportion keeping their tank a constant in all respects but, hey, striving for perfection isn't a bad thing, right?

Most short term stresses they will survive but if those stresses are longer term they won't survive. Things such as UV or high temp. Which is why we acclimate and monitor. Sure the corals were able to survive in that temp but the water cooled at night and they can't really survive more than 2-3 days at high temps. (search info on the 1998 and 2002 Great Barrier Reef bleaching events) Plus I'm guessing those corals weren't using much energy on growing, just surviving. At the same time I'm guessing the drop in temp was hitting the thermocline in the water which is at depth so those corals probably see less variability than those at the surface. Small daily shifts are usually where people get picky but they probably won't do much damage. The large swings will more than likely bring stress and the coral won't thrive.

Bottom line: coral reefs have seasonal variability and changes due to weather and forces of nature. Sure some or most of the corals survive those changes but at the same time some of the corals don't fare well and die. Who wants to say that "most" of their corals survive or show great growth?

[greenbean36191]

I always find it ironic when there's a report about how coral reefs are in peril, people write it off saying that corals are a lot tougher than scientists give them credit for, yet we give them a lot more credit than hobbyists do.

At the same time I'm guessing the drop in temp was hitting the thermocline in the water which is at depth so those corals probably see less variability than those at the surface.

Except in shallow, restricted water this generally isn't the case. On exposed reefs, the opposite pattern is usually seen due to internal waves sloshing sub-thermocline water onto the reefs. 3-5 degree variations throughout the day occur on most reefs and some refs see about 15 degrees within a few hours in the upper 30 meters.

The large swings will more than likely bring stress and the coral won't thrive.

There is no evidence suggesting this is the case, even on reefs that see changes of 12-15 degrees within a few hours.

What does clearly harm corals is exceeding the maximum acclimated temperature by 2-4 degrees F. Hobbyists generally don't make the distinction between temp variations within the normal range and outside of the normal range though. They figure if they had a 4 degree temp spike and things look bad then that means that any 4 degree variation is bad news.

This can actually work against hobbyists since it's generally accepted that corals from more variable temperatures are more resistant to thermal stress.

Sure some or most of the corals survive those changes but at the same time some of the corals don't fare well and die. Who wants to say that "most" of their corals survive or show great growth?

Some corals fare poorly and die during extreme events. There is no evidence that regular variations within the range they're acclimatized to are harmful to any of them. It's also not necessarily true that there is any reduction in growth. At least some species show temperature independent growth rates. They grow the same whether it's hot or cold or whether the temperature is variable or stable.

[Paul B]

Soultwater I have about as many dives and I agree with you.
I don't have a refractometer for that reason. There is no real normal salinity in the sea.
Here in the North east of the US our salinity is very low, sometimes bordering on brackish and in the summer I collect a wide variety of tropical fish. The water in my own reef varies greatly during the year. I try to keep it as constant as possable but with accidents, power outages, leaks etc. it is not always possable. My temp ranges from the seventees in the winter to the low 90s in the summer. Again, I am not trying to make variations on purpose but in almost 40 years of salt water fish keeping, I have never lost an animal to salinity or temp variations.
The sea also experiences typhoons which I try to occasionally replicate in my tank. The corals evolved with them and they are normal and in my opinion, needed to rejuvinate the rocks.
Just my opinion.

[IslandCrow]

The sea also experiences typhoons which I try to occasionally replicate in my tank.

OK, Paul B, you've piqued my curiosity. What's your process for replicating typhoons? I'm just imagining all those poor little gobies going on the ride of their lives inside you tank.

[Paul B]

I pack up the tank and fly it to Tahiti
OK not really.
But I do occasionally use a diatom filter and I put a restriction on the preasure hose which makes it into a powerwasher that I use on the gravel and all of the rock surfaces that I can reach.
You would be amazed what comes out of rock.
I feel that this is a big factor that allowed this tank to get so old.
I don't have a DSB so I can stir up everything

[KafudaFish]

Last week I reached into my tank and it was ice cold. I checked the thermometer and it read 62 F. I have no idea how long the tank was sitting at the temperature but it could have been a week plus.

I too have been cleaning my tank with the hurricane method and it is scary what is getting pulled out.

[jflick345]

I wrote my response quickly and wasn't very clear on what I meant by a few statements.

Originally Posted by jflick345

At the same time I'm guessing the drop in temp was hitting the thermocline in the water which is at depth so those corals probably see less variability than those at the surface.

Originally Posted by greenbean36191

Except in shallow, restricted water this generally isn't the case. On exposed reefs, the opposite pattern is usually seen due to internal waves sloshing sub-thermocline water onto the reefs. 3-5 degree variations throughout the day occur on most reefs and some refs see about 15 degrees within a few hours in the upper 30 meters.

I should have thought my statement through a little more thoroughly. haha Any coral near the seasonal thermocline will obviously see a decent temp swing. I was speaking from experience diving in The Bahamas and where we hit it. That is simply a "duh" moment. If a coral is living anywhere near the seasonal thermocline why wouldn't it see a normal variation in temp? This is what happens when someone starts typing before thinking through what they're saying. haha Thank you for clarifying.

Originally Posted by jflick345

The large swings will more than likely bring stress and the coral won't thrive.

Originally Posted by greenbean36191

There is no evidence suggesting this is the case, even on reefs that see changes of 12-15 degrees within a few hours.

Again, I suppose that thriving compared to a tank with a stable temp is difficult to prove. There are examples of all sorts of exceptions in the ocean but how many people do that in their reef tank? The statement was based on the idea that many of the corals kept in the hobby are from shallow tropical waters. A temp swing every day from 65-80 or 72-84 daily is probably fine for reefs in some parts of the world but I assumed most of the corals kept in the hobby aren't used to that kind of daily swing. Maybe misguided but seemed like a logical assumption at the time.

Originally Posted by greenbean36191

What does clearly harm corals is exceeding the maximum acclimated temperature by 2-4 degrees F. Hobbyists generally don't make the distinction between temp variations within the normal range and outside of the normal range though. They figure if they had a 4 degree temp spike and things look bad then that means that any 4 degree variation is bad news.

Couldn't have said this better myself. I should have done a better job clarifying what I was talking about. I appreciate you sharing your expertise. I was working off remembering articles and books I read probably 3 years or so ago. I think it's time I start brushing up for grad school and refresh my knowledge instead of trying from memory. It seems like there's always someone on here willing to make the effort to correct you.

[Soultwater]

Originally Posted by Soultwater

I think it would be better to not have such a dramatic change

just quoted myself


WOW good info from people smarter them me LOL

I was just going over my experiences and this made me think … Once the smoke cleared I thought I would post my experiences and see what people thought.