Photo by Eric Lafforgue I was recently asked a few questions regarding trace elements and my current dosing regimen. I am not completely ready to share that, but here are some ramblings from that initial dialogue. Dana Riddle has an article coming up on trace elements and coral coloration that we all should be looking forward [...]
Photo by Eric Lafforgue
I was recently asked a few questions regarding trace elements and my current dosing regimen. I am not completely ready to share that, but here are some ramblings from that initial dialogue. Dana Riddle has an article coming up on trace elements and coral coloration that we all should be looking forward too.
Provided a near NSW parameter salt is used, trace elements can be replenished through frequent water changes. But are they replenished to proper levels? That’s an extremely difficult question to answer and will vary from tank to tank. Trace element addition should be based upon utilization by organisms and removal via filtration. (For more information on this see Randy Holmes-Farley’s piece on Low Soluble Metals) Testing of these levels at a hobbyist level is a crap shoot and at a professional level it is expensive. For this reason, many opt for the mantra, ”if you cannot test it, do not add it.”
With the wave of carbon dosing (e.g. Zeovit & VSV) and the recent popularity of the Balling Method we are begining to see an increase in trace element additions by experienced aquarists seeking the best coloration in their corals. (More info on the Balling Method here.) Most of the information on the benefits of these trace elements is strictly anecdotal, e.g. iron enhances greens and potassium iodide enhances blues. However, some of the information regarding the lightening effect that certain elements have (via expelling zooxanthellae) is well documented by scientific literature.
Why would aquarists care about expelling zooxanthellae? That is a damning question. For aesthetics, less zooxanthellae algae within the tissue of Acroporids results in increased coloration. The dreaded “brown” is generally caused by the corals symbiotic zooxanthellae algae. If this is removed the pigments underneath can show better… or in some cases the lightened palette provides a better contrast. Purple on white or purple on brown?
At one point a test was done on a specific proprietary liquid supplement that caused coral tissue to lighten in order to enhance coloration. Supposedly it was found to contain copper. Some where surprised by this, and scared because of the toxicity we associate with the word. Copper is known to be lethal to inverts and doubles as a treatment for Cryptocaryon, aka Ick. However, copper is a natural trace element found in the ocean, and correspondingly so in synthetic salt mixes. Little do most aquarists know, many of the “inputs” that we add to our tank, such as fish food, can contain copper. Copper and other metals are also incorporated into protective anti-oxidative enzymes within coral tissues.
The lightening effect that this copper containing product has, should be no surprise to scientists in the field. Numerous studies have been done on the bleaching effect that heavy metals can have, such as Copper and Zinc. Most of these were performed to test the effect pollution has on coral reefs. The fact aquarists are adding what many consider a pollutant is ironic and laughable, but it also raises the ethical implications. Is “unnaturally” altering coloration a good thing, something that aquarists should strive for? That’s for you to decide, but worthy of consideration.
Back in 1989 a study revealed iron toxicity levels for Porites lutea [Abstract here], but since then it seems most of the focus has been on Copper and Zinc. [Sidenote, I stumbled upon this interesting study that explains the orange bands in dead coral skeletons often seen in coral sold for fish only decor. In my early years in the hobby I always wondered!]
In 1997, Ross Jones of James Cook University in Queensland Australia performed a study titled, Zooxanthellae loss as a bioassay for assessing stress in corals. I believe this was the first study I read that really perked my interest in “Heavy Metals”. In this study it specifically addresses the effect of Copper on zooxanthellae. For those without database access, this is fortunately available online in PDF: Jones ’97.
From it:
“Branch tips of Acropora formosa from Test 1 exposed to 80 µg 1-1 copper turned from a normal brown colour to a lighter colour within 6 h, and to a light tank colour by 24h.” (Note, at this strength the coral died.)
“Bleached tips returned to the reef after the experiment gradually recovered their colouration, suggesting the loss of zooxanthellae observed during the studies was a sublethal response.”
Also worth noting, the release of zooxanthellae from copper toxicity was greatest during daylight, and reduced during darkness. For Jones daylight expulsion was two times greater than night time. Despite this rapid increase during the day time Jones states that the rate of expulsion was still less than the rate of zooxanthellae produced by cell division, hinting at the animals resilience to such stressors. Earlier studies have shown similar results from Pocillopora damicornis and Montipora verrucosa.
Another study in 1993, by the University of Singapore looked at Copper and Zinc Concentrations on zooxanthellae growth. Again, I bring this study up because it is available to the public here: Cu and Zn on Zooxanthellae. This study finds that Copper and Zinc act “synergistically in their toxicity to zooxanthellae.” Meaning, in the presence of Zinc less Copper was needed to reduce zooxanthellae growth rates (and vice versa.)
If you are wondering how trace elements can enhance or modify the coloration of SPS corals, take a peak at those two studies. If you search under terms like “Copper Zooxanthellae” under any scientific journal database there are countless others, some of which go into the role of Copper-zinc superoxidase dismutase, “Cu-ZnSOD”.
Keep in mind expelling zooxanthellae is not the only way to alter coral coloration. Water quality and lighting also play a crucial role. The biggest question I find asking myself, should we be expelling the symbiotic algae that these corals need from heavy metal supplementation? Now there is nothing natural at keeping these animals in a glassbox, but at what point do we cross the line… or have we cross the line by just having an aquarium?
I am currently experimenting with a few trace elements and some of the results are extremely interesting. The heavy metal toxicity seems to be very coral dependent, or at least based upon the few Acropora species that I have experimented with. That is put on hold at the moment, as last week I found AEFW again. More on the dosing and AEFW to come.
