As I get my tank back on track, I'm focusing more than ever on how to maximize coral growth. Specifically, I'm looking at SPS growth, although don't want to sacrifice long term health (in terms of weaker branches, lower tolerance to changing conditions, etc).

I'd like to start a discussion on what the primary (and even secondary) factors affecting coral growth. I'm looking for discussions about any of the following:

- balanced levels of calcium, alkalinity, and magnesium
- the proper amount of light (more than just watts/gallon - PAR, depth, light types)
- the proper amount of flow (turnover is a poor indicator. Has anyone done a water velocity test to know what it is in cm/s?)
- use of strontinum
- the possiblity of dosing nitrates (using potassium nitrate)
- anything else that may be related

Let's see some good, intelligent discussions. And please reference when possible. If we get really involved into one topic, I'd be happy to break those posts off into another thread.

I found the thread over on ReefCentral called Let's talk about Alkalinity, Calcium, and Magnesium in an SPS Tank (http://www.reefcentral.com/forums/showthread.php?s=&threadid=1179702), and they outline some good numbers for maximizing coral growth. Specifically:

Alkalinity: Most people recommended that we keep out Alk levels at 10-12 dKH. Over time myself and many others, keeping primarily acroporids as well as other SPS, found that the high end of the dKH scale is not always better and that keeping alk closer to natural sea water levels of ~8dKH yielded good, if not better, results for SPS. My personal experience is that I found much less incidence of RTN and my pH became just as stable when balanced with the proper levels of calcium and magnesium. So my recommendation is to keep alk around 8-9 dKH for keeping acroporids. Another nice benefit of lower alk was less precipitate on heaters and pumps.

Calcium: And I have had the best success with high levels of calcium between 450 and 500 ppm. I feel that this allows me to get a very good growth in my aquarium. I had kept my calcium levels at around 360-380 for a few years and while this did not cause any problems, my growth wasn't anything to brag about. High ca levels really pushed my growth up a huge notch. Note, that I keep low levels of alk in my tank so that helps me to keep a higher level of ca in the aquarium as well.


Magnesium: I personally like to maintain magnesium levels at 1450-1500 ppm. For me that has worked out best. it allows me to easily maintain my alk and ca levels and my corals seem to do best at this level as well.
[...]
The primary benefit of Mg is that it allow calcium and bicarbonate levels in the water to exist at supersaturated levels. In laymen's terms, having high Mg allows you to maintain higher Ca/Alk.

Because Ca and bicarbonate are supersaturated, they are always ready to fall out of solution. This is the abiotic precipitation that every talks about on heaters, pumps, and solid surfaces. As calcium carbonate forms on these surfaces, Mg is also able to bond with it. By doing so, Mg blocks Ca and bicarbonate from being able to attach, significantly slowing the rate of precipitation. If you let Mg drop, you have to pour in more and more Ca and Alk supplements, and precipitation becomes more and more of a factor.

I don't think corals deliberately use (or require) Mg, it's more of an incidental pick-up while building their skeletons. But, maintaining Mg levels is necessary to hold Ca and Alk levels where you want them.


So... taking all this in, we get the following target ranges:

Alk: 7-8 dKH
Ca: 450-500 ppm
Mg: 1450-1500 ppm

The question becomes- what is "balanced"? Does anyone know how to show that with a given calcium level, the carbonate hardness should be X dKH? Can that be shown mathematically?

I'll touch briefly on a few of those points....can't really site too much because most of the talks I was in were mere speculation.

Balanced CA, ALK and MG. These are just KEY to making any tank grow. As to what exact level per each is required...? I do know the more stable/constant they are, the better it is for the coral. I know that sounds obvious. I did notice a huge amount and now a steady growth rate after I put my CA reactor on.

Proper light- I'm not one to follow norms here, obviously if you know my tank. I'm getting great growth and color from my 175's I do largely believe its due to the reflector and how well they utilize all available light. However this is a MAJOR draw back for me. I've fried many corals that I've just put in my tank. There are a huge room for error here with light intensity.

Strontium - I had been dosing it back in the day....rumors floated that it "beefed" up the core structure of a coral. Yes this is true, but to what extent? I've also "heard" that dosing it will stunt the growth of the corals, mainly because they are focusing on building such a strong core. There have been a few talks over on RC about this and it's kind of a "top of the fence" debate. Some believe in dosing it, others believe that a simple water change is ample enough. Perhaps now that I have my CA reactor on line, I should try a little test to see if growth really is stunted?

If anything, maybe a little Fiji showers would work best for you ;)

As far as that mathematical equation, I've always used this calculator to "balance" my levels. But who knows if that "balance" is right? Seems to work for me though.

http://jdieck1.home.comcast.net/~jdieck1/chemcalc.html

Hmm. Something doesn't add up. I played around with that chemistry calculator, and ballanced Calcium and Alkalinity is:

475ppm Ca and 16 dKH

So.... how were the guys in the post above able to pull off 450+ Ca, but keep the Alk at 8 dKH?

I tested my water duing lunch. Looks like I'm getting closed to a balanced mix:
Ca: 420 ppm
Alk: 10.5 dKH
Mg: 1375 ppm
pH: 8.14

My guess is they got the levels they wanted in the tank then kicked on the reactor. If your levels are where you want them, and the reactor is kicking balanced out, it should "maintain" the levels in your tank where you have them. Thats why its always best to get your tank where you want it before adding a reactor. At least, thats my understanding.

wouldn't raising salinity help coral growth? I'm not sure where you sit at salinity, but they will likely grow faster at 1.026+s.g .than the normal recommended 1.023ish s.g.

1.023 is for just fish. Most reef keeps are at 1.025-6 Any higher and I would think it would harm the corals. Could be wrong tho.

When I first raised my tank to 1.026 (from ARC advice), I did not realize my hydrometer was off, and ended up killing just about all of my fish, but my corals had more growth in those 3 days than I had seen in weeks. So I brought it back down to 1.023. Turns out 1.023 on my hydrometer = 1.026 in reality. so my s.g. went to about 1.029, and the corals seemed to love it; I could not tell you if this would be for the long term, or what level is best, but just a tid bit of personal experience.

Reefs from around the world range from 1.017 to 1.040 (Persian Gulf), according to The Reef Aquarium, Vol 3, Delbeek & Sprung. They also state that the "acceptable range ... for a reef aquarium is between 1.017 and 1.032. They don't talk about any side effects - only to mention that stability is key.

I found some references on the web, particularly an article by Ron Shimek "Reef Temperature and Salinity Levels" that talks about optimal levels, but can't find the actual article. He states that 84 degrees yields the maximum growth (due to biological processes being sped up), but at the risk of being very close to the edge of the coral's tolerance.

I personally don't see how increased salinity would provide any benefit. Neither does Randy Homes-Farley (http://reefkeeping.com/issues/2004-05/rhf/index.php), so I'm going to stick with my current salinity (1.026).

I have found that my stoneys grow faster when my phosphate is around 0.01 as opposed to around +/- 0.024. I'm not sure if trates have the same effect or not, but I keep them about 0.5.

I'm ok with my growth (but just ok). I wonder if my heavy than average bioload contributes to fast growth or slower growth. I'm guessing slower. I would like to be able to kick it in a bit and get some maximum consistent growth.

These numbers match what I test, so here are my current parems:

oh yeah, temps at 82! Temp was 78 until about 8 months ago. It seems that growth has picked up a little. (that would be an assumption)

Growth will increase with the raise of temp. Its believed that the corals metabolism increases with a higher temp, thus converting more light into food to grow.

The whole "higher lighting is better" is a tricky ball of wax though. It is so coral dependant. when Dana Riddle spoke to the club, I was utterly amazed at the photosatuartion curves he provided for some corals. Many corals we love (supermna, digitata, etc) has maximum photosysnthetic values at like 300 PAR or so. I dont remeber the bexact values for exact corals (I sure someone took notes and posted I we search this forum), but I just remember the values were so much lower than what I anticipated. After that peak value, the zooxanthellae clades in these corlas started to get photoinhibited.

So, to make a long story longer, I dont think its as easy as saying "the more light, the better". For some corals like torts, or Tridacnids, likely so, but for others, you be actally harming growth ans survival. I sure Riddle has this published on www.advancedaquarist.com (http://www.advancedaquarist.com) somewhere too.

Too true sir, too true. Now whats your stance on the whole, "corals only really need 5hrs of light" I think there was a topic like this on RC saying corals only really need 5 hrs a day of our lighting, any more than that is a waste. basically they were saying in the wild there isnt "that" much direct light on corals all the time, like in our tanks. And we're pretty much wasting money running our bulbs so long because the corals will use up/exhaust their limit of intake from the suns/lights energy faster with full on intense light......did any of that make sense? lol.

I remember that talk by Dana, and I too was pretty blown away by the results. However, one thing that he didn't cover was photoinhibition vs. coloration and if the the two are related. People often state that the coloration is the 'sunscreen' of the coral, to protect the zooxanthelae, but I'm not sure if anyone actually knows.

So, with that in mind, is it possible that a coral may hit it's photoinhibition at a certain PAR, then start to be more colorful after that? And is that state detrimental to the coral? I did say this was a topic about maximizing SPS growth, but I also don't want a tank of brown corals (nor do I want 5500K bulbs!).

Too true sir, too true. Now whats your stance on the whole, "corals only really need 5hrs of light" I think there was a topic like this on RC saying corals only really need 5 hrs a day of our lighting, any more than that is a waste. basically they were saying in the wild there isnt "that" much direct light on corals all the time, like in our tanks. And we're pretty much wasting money running our bulbs so long because the corals will use up/exhaust their limit of intake from the suns/lights energy faster with full on intense light......did any of that make sense? lol.

Thats a loaded question. Corals do probably only need 5 hours of light, but does 6 to 8 hours impair them? My answer would be no. I dont think corals can regulate or "turn on and off" the zooxanthellae for energy production. What happens when a corals gets overilluminated? It either bleaches or burns from oxygen toxicity (the by product of the photosynthesis). That is what happens to deep water corals that get overilluminated. So, what would enable a shallow water coral to turn this on and off? Furthermore, I cant see it as being benign either. In my mind, I understand this as black and white- they can either make energy (ATP) from photosynthesis (and the associated byproducts), or the can't. I cant see any photosynthetic organism get hit with light and ahving it be beneficial at one moment, and then benign the next. But I am no coral biologist.

Personally, I think comparing our aquariums to oceanic conditions needs to be erased from consideration. The differences in variable is so intense, I dont see the purpose in doing it. We can certainly attempt to emulate, and possible learn acceptable conditions, but the type of comparison mentioned (corals in the coean only get 5 hoyrs of direct light- say who? Who measured that where the coral was collected? Does the fact that it mightve been 9000 PAR or maybe 150 PAR play any role?) is piointless and impossible to relate.

So, the question boils down to: are corals that are over-illuminatedimpaired? Quite possibly. However the only way know this is to test it in your system, with your lights, and your corals, at different phtoperiods. Everything else is ubsubstatiated speculation. IE- My emperor angel doesn't eat corals- does that mean that I can make the claim that they are reef safe?

I remember that talk by Dana, and I too was pretty blown away by the results. However, one thing that he didn't cover was photoinhibition vs. coloration and if the the two are related. People often state that the coloration is the 'sunscreen' of the coral, to protect the zooxanthelae, but I'm not sure if anyone actually knows.

So, with that in mind, is it possible that a coral may hit it's photoinhibition at a certain PAR, then start to be more colorful after that? And is that state detrimental to the coral? I did say this was a topic about maximizing SPS growth, but I also don't want a tank of brown corals (nor do I want 5500K bulbs!).
Ahhh....coloration discussion. Number 593 on my pet peeve list. I HATE when someone says, "your corals are browned out? Its from excess nutrient, put some GFO in there and they'll get their color back." Hogwash and poppycock. Yes, nutrient availbility will play a part in zooxanthellae growth and localized population within the coral, and yes, nearly all zooxanthellae are brown. But that is a very incredulous leap of faith. It may be true, but it just as likely may be untrue.
Coral coloration can come from numerous different sources. For example, green can come from excessive UV exposure, while other coral biosystem clades, have intrinsic pigment, unrelated to water conditions really. Pigmentation clades operate at certain conditions (temperatures, wavelengths of light, other coral conditions), which tend to make certain clades specific to certain corals. These clades with tolerate different lighting, which corresponds to the corals tolerance.

But, I digress, does good growth equal bad color. No way. I think the two have no direct relationship with one another really. I think both are influenced by the same conditions (flow, light, temop, etc), but they coincidentally thrive at these conditions, not because of dependence.

Yeah man I hear what you're saying. That was just one of the many talks on RC that showed a lot of interest.

Yeah man I hear what you're saying. That was just one of the many talks on RC that showed a lot of interest.

For what its worth, once I get the lumenbrites in order (if Alan can ever get off his lazy, Hawaii vacation going, "I work a lot" butt, and build my canopy!), i obviously ahve to start with a very small photoperiod, but I was only going to run the two side 400s for 5 or 6 hours, and then the central 400 for closer to 7 or 8.

I'd start with 4 hrs for a week. Then go up an hr ever 2 days till you're where you want to be. Interesting thought on running the lights. I had thought about that but didn't really seem appropriate....no real rhyme or reason tho. For the fun of it tho, I have my lights turn on and turn off from left to right with a 1/2 in between. I think they run for 8hrs each.

yeah they do, turn on at 4, 430 and 5. Turn off 12, 1230 and 1

I have tried different photoperiod over the years and have seen very little if any difference in growth or coloration in between 6-12 hours. I tried 4 once and did see stunted growth. So bottom line is I use 6 because I found it to work just as good as 12 and I use half the electricity!.

I run my halides 8 hrs and I think 10 or 11 with actinics.