[Coral-List] Rebar & algae

Michele & Karl michka at fellenius.net
Fri Dec 2 01:32:05 EST 2005

Coral listers,

I run a small ocean-based coral farm that focuses on Acropora spp.
cultivation for the aquarium trade over a 4-6 month grow-out period. It is
located in Vanuatu and is relatively new. We start with 3-4cm pieces and
allow them to double their height and to become 'bushy' before export. We
also provide some stock for re-planting purposes through local dive
operators on popular dive sites.

We have experienced considerable algae build-up on our trays, some of which
may be blue-green. The environment is relatively pristine, with no obvious
point source discharges. The reef appears healthy.

My question is if anyone knows about possible contributions by regular rebar
(steel rod, non-galvanized) to nutrient loading as it rusts over a longer
time period? We had no issues for a long time and then in conjunction with a
couple of blooms and rustier rebar we were covered in algae starting last
July through to the present. Ironically, the water was a few degrees cooler
in August than it is right now. The reef did not appear to be impacted in
any way. It is just the mesh tray structures attached to the rebar and the
small rock bases with the coral that are attached with cable ties to the
mesh, that are affected. The mesh, in contrast with the rebar, is
galvanized. The rebar and mesh trays are in 4-6m of water.

So we are now experimenting with galvanized rebar, and also going deeper.
Less growth, but also less algae, we hope. The galvanized rebar is
expensive, so I only really want to pursue this direction if others might
have observed algae growth under the right (wrong) conditions associated
with proximity to rusting metal structures.

Thanks for any comments.

For your info. we are trying to ID species as much as possible using a photo
microscope on dried skeletons and comparing with J. Veron's "corals of the
world." Photos are on the website below. The code for the corals is the
volume and page number of a species. For example, A. vaughani on page 268
would be entered as code 1268 to gain access to the photos. If anyone would
like to see if we are growing a particular species, just enter the code and
if photos come up then we are. If not, we will be later :) We'd like to be
as accurate in our species ID as possible, so if anyone has any comments
here on right/wrong ID then I'd love to hear it. This ID will hopefully lead
to better ID in the industry and a healthier value & respect, for the coral,
at the retail end. It might also allow, at a later date, for better CITES
export paperwork labels than just "Acropora spp."

Another point I'd like to mention is that our facility is open for research
access if anyone would like to coordinate any future research/student
projects. It is our long term plan to have research housing available on

Karl Fellenius
Reef Solutions Vanuatu

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