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Unread 10/17/2017, 02:47 PM   #213
Scrubber_steve
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Join Date: Aug 2016
Location: Down Under
Posts: 676
Quote:
Originally Posted by Timfish View Post
You're welcome! Delbeek and Sprung in "The Reef Aquarium" VOL III discuss the decision by scientists at the ReefHQ Mesocosm on the Great Barrier Reef Marine Park Authority in Australia to remove their algae scrubber after 16 years to deal with water quality issues. Dr. Adey's research that led to his development of algae scrubbers was a huge step forward in our understanding how reefs work but research since then, particularly the role of DOC and it's influence on microbial processes, has raised serious questions about the long term use of both algae scrubbers and carbon dosing.
Hi Timfish. Not wanting to sound rude, but what you've stated above could not be further from the truth in regards to why the Algae Turf Farm (ATF) was removed at the Great Barrier Reef Marine Park Authority (now Reef HQ & Coral Reef Exhibit) particularly in regards to dealing with water quality issues. Lets look at the facts concerning the algae scrubbers & the measures taken to improve water quality to improve coral mortality rates.

The algae scrubbers were in operation from 1987 to 2002 and were removed from the Coral Reef Exhibit (CRE) at the GBR Aquarium because -

1. Most importantly, the Algae Turf Farms effects on CRE filtration were negligible, especially when compared to the CRE’s overall internal algal mass productivity. The ATF only accounted for 0.1% of systems overall algal mass)

2. they were too labour intensive (algae removal & servicing of troublesome dump buckets). The ATF consisted of 70 shallow PVC trays approximately 2 m in length and 1 m in width.

3. The pvc used to build the scrubbers was leaching toxins into the water. Possibly because they were affected by direct sun light. I know this because I was given a personal behind the scenes tour of the Aquarium in March this year by the Aquarium's Curator.

Now lets look at the actual measures taken to improve water quality to improve coral mortality rates.

A significant shift occurred during 2002 with how the CRE was maintained when the aquarium was closed to the public for almost five months to maintain and upgrade the facility.

The CRE history is divided into two periods –
The “Oceanic Water period” (pre-2002) Average corals survival rate was only 20% to 30%

The “Estuarine Water period” (2002 to present) corals survival rate increased to 70% to 80% (possibly higher now).

The changes made to the systems maintenance that were considered most critical to improving coral survival were –

1. The switch from using priori ultra-clean oceanic water, collected offshore by barge, to using ‘less pure’ estuarine water collected on the incoming tide from the Ross Creek to increase nutrients and provide an external source of plankton.

2. The removal of internal mechanical filtration (three large sand filters). This improve overall tank health by avoiding ‘over stripping’ the water column of particulates and encouraging plankton production, greater food availability, and larval settlement, especially during spawning periods

3. Internal circulation was increased.

4. The use of calcium chloride to raise average calcium levels (~ 250 mg Ca2+.L-1, to 420 mg Ca2+.L-1)

https://www.burgerszoo.com/media/560570/chapter-26.pdf

https://www.burgerszoo.com/media/560502/chapter-9.pdf


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