[Coral-List] Corals and metal poisoning

Borja Marcos borjam at gmail.com
Mon Oct 29 05:46:28 EDT 2012


I hope my message isn't misinterpreted, this is _not_ a call for help
about an aquarium. Read on, please.

I've had a strange problem in my aquarium since last Summer. Suddenly,
mostly green pigmented colonies of "small-polyp" corals, Montipora
digitata and a "plate" Montipora, Stylophora and Pavona cactus have
almost been wiped out. Before the problem, these colonies had shown
healthy growth (4x increase in size in 8 months). Curiously, the
problem was less serious for orange-red, pinkish and violet  "plate"
Montipora colonies.

It's been rather puzzling, because the damage seemed to be worse when
keeping the proper pH and alkalinity. The Pavona colony showed signs
of stress (lots of mucus production) at the end of the day, with the
peak pH. Seems the corals became "ocean acidification friendly"
(pardon the pun).

Anyway, last week I finally found the likely culprit. I was using
magnet attached clips to hold dried algae for the vegetarian fishes,
and, to my shock, it turns out the magnets aren't properly sealed and
two of them were severely rusted and corroded. I wonder if epoxy
coatings have been invented or I live in a parallel universe, who

I don't know much about the magnets, apart from my guessing. The
manufacturer refused to tell me their composition, but I can guess
they are FeNdB magnets, and the manufacturer swears they have no Cu. I
can guess that claim is true, because I haven't seen a dramatic
decrease in the smaller invertebrates (copepods, ostracods, amphipods,
mysiids, polichaetes), just tanaids, and it could be well due to
predation by fishes, or just an "ecosystem" adjustment.

Once I have discovered the likely cause, removing the magnets and
performing daily partial water changes should solve this issue, and
that's what I am doing. After several days, I think I have noticed
that the Pavona is producing less mucus at the end of the day, which
should be a good sign, we'll see.

Is there anyone here, studying the effects of metal contamination of
invertebrates, who would find samples useful? I have three magnets
(one of them isn't as severely corroded, it wasn't used so often) and,
unfortunately, a lot of Montipora and Stylophora skeleton (the Pavona
seems to be still alive, although almost bleached).

If someone is wondering about water temperature and the Summer, the
peak water temperature was 29 degree centigrade, similar to the
previous Summer when the tank had been recently set up and the corals
were growing like crazy.

Of course I admit I am curious about the outcome, but I am wondering
if these samples can help someone to find a "missing dot" in a line,
so to speak.

Needless to say, I'll post for free (it's cheap anyway) and probably
Europe would be much easier.

Best regards,

Borja Marcos.

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