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Artificial oyster rocks can replace reef rocks used for biological filtration in marine aquariums

dw1305

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Hi all,
This came out of the discussion on <"is expensive bio media worth it?"> in freshwater tanks, but it looks quite interesting.

I know nothing about marine tanks, so any comments would be much appreciated.

Cohen, F., Cabral, A., Lillebø A & Calado, R. (2021)
<"Relieving pressure from coral reefs: Artificial oyster rocks can replace reef rocks used for biological filtration in marine aquariums">
Journal of Cleaner Production, 325, <"Redirecting">.

Natural reef rocks have been harvested from the wild for decades to supply the marine aquarium trade. These rocks have been used in home aquariums mostly as substrate to safeguard biological filtration, especially for nitrification. Producing artificial rocks can be a sustainable alternative to the harvest of natural reef rocks from the wild, thus promoting coral reefs conservation. Nonetheless, there is a lack of scientific knowledge on standard formula to prepare artificial rocks, as well as on their potential to promote nitrification. The use of oyster shells, a by-product from oysters’ aquaculture, appears as a promising ecological and economic approach to produce artificial live rocks. Thus, we aimed to develop a standard formula to produce artificial rocks made with oyster shells and test its potential use as a substrate for biological filtration in marine aquariums. For that, we prepared artificial oyster rocks with different sized fragments of oyster shells and compared their ability to promote nitrification of ammonium nitrogen with that of natural reef rocks and fragmented oyster shells. The formula was set at 1 g of dried cement (white Portland cement with limestone) per 3.1 g of dried oyster shell fragments. The volume of water used to prepare this mix was set as 50% of the cement weigh. Our results indicate that artificial rocks made with oyster shells and cement display an ability to promote nitrification similar to that of natural reef rocks, promoting a slight decrease in pH and without releasing PO4–P. All treatments with substrate were able to oxidize up to 21 mg.L−1 of TAN (total ammonia nitrogen, initially added in the form of NH4Cl) within a 48-h interval. In other words, it is possible to safely assume that all tested substrates oxidized an average of ∼4.4 ± 0.1 μg of TAN.g−1.h−1. Thus, our results support that artificial rocks made with white Portland cement and oyster shell fragments are a sustainable option to safeguard a suitable biological filtration in marine aquariums......

cheers Darrel
 
This is awesome, thank you for sharing! I'll have to make some moulds for my own custom-shaped oyster shell reef rock when I try marine in the (hopefully near) future :D
 
People have been doing some pretty crazy things with Portland cement, rock salt and water softening salt, to create artificial live rock. It can look pretty impressive and comes with the benefits of no nasty hitchhikers or depleting rock from the ocean. You do need to soak it for a while for the alkalinty to stabilise though.
 
Hi all,
This is awesome, thank you for sharing!
I'm going to assume that you could access the full paper OK?
it can look pretty impressive
Which reminds me that I should have put the picture in:

Artificial_Coral_rock.jpg


The "Artificial Rock - Small shell Fragments" performed more successfully (out of the oyster shell rocks) at the start of the experiment, but by 20 days there was no difference in nitrification between all treatments (fragmented reef rocks (FRR), fragmented oyster shells (FOS), and artificial rocks made with small shell fragments (ARS), medium shell fragments (ARM), and large shell fragments (ARL)).
pretty crazy things with Portland cement, rock salt and water softening salt
Salt to create the holes in the "rock"?

cheers Darrel
 
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Salt to create the holes in the "rock"?
Exactly the different size salt crystals used (rock salt and water softener salt) result in smaller and larger holes in the final rock after soaking. It's a very clever solution and much better than flying boxes of damp news paper covered rocks around the world, hoping that some of the life inside will survive.
 
I'm going to assume that you could access the full paper OK?
Not right now, but you added the proportions of the mix in the quote in so that's perfect! I'll be doing a marine project with a friend that works for a university part time so I should be able to access it via them too. Super useful stuff.
 
Hi all,
Not right now, but you added the proportions of the mix in the quote in so that's perfect!
If any-one does want the full paper? PM me your email address and I can send the pdf.

I also know that you can buy oyster shell fragments cheaply, in different grades, as <"Chick(en) Grit"> *

* if the link stops working that was £2 per kilo at P@H (also £2.50 per kilo at Wilko's)

cheers Darrel
 
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