Concrete products and coral grow out.

Concrete products and coral grow out.

Postby Oceanarium » Sun Dec 30, 2012 4:11 am

Looking for opinions and information on what might be negative effects of concrete products to reef building corals within re circulation systems. Attempts to find information leads to conflicting results. I see the concrete blocks are now popular to build and rehabilitate wild reefs. I also know of an abalone farm that moved away from the concrete products they used because of tests revealing certain substances being leached.

A bit of background, I have been using concrete and aragonite mix to make the base we culture our corals onto for many years. Researched a lot in the early days about curing etc and came up with a product that worked well for us. Initially I had a wild collect operation, the culture side R&D for a future expansion to a full blown culture operation. A few years back we started the new culture operation. This involved several systems dedicated to live rock and coral grow out, in order to get the government approvals conditions place on us was that no natural rock could be used to grow our products. We settled on the concrete option.

Each system as it came on line had a large amount of concrete rock, to become live with time. We added all the bits as required coralines, sponges, bacteria etc. Simultaneously we added corals all glued to fresh but small concrete stones. The systems all took a long time to dial in at least a year before I had them performing adequately well for all coral types. Things chugging along fine for several months selling nice cultured corals :mrgreen:

Then we start to do a bit of live rock sales, at first only small batches of a few boxes here and there. replacing the sold rock with new base rock to become live. We notice difficulties in our coral culture in attempts to keep all corals growing well, things like loss of axial polyps on SPS, set backs in montipora's etc. Change a few things fiddle around for several weeks, things improve. This happens several times and in different systems.

By now i am becoming suspicious, but still we have been successful using such products for many years though never quite in such volumes. I am mixing concrete and making rocks now most days of the week, curing them for several weeks then placing them for 2-3 months in a 2500ltr tank that stores our waste sea water from water changes this is emptied of 1000ltrs every week.

Then we get some big live rock sales and one system in particular gets a few hundred kilograms of fresh rock added... The SPS all loose axial polyps sensitive corals like monty in particular are hard hit with colony's receding even tougher corals as Serriatopora with some color morphs also receding.

By now I am certain the adding fresh rock has effects, I decided to wait for the corals to improve though not to add any more rocks. After several months things have improved, though still not quite right. I bit the bullet and remove all the freshest concrete rocks out and replace with a quarried rock. within weeks axil polyp production is very good.

As a result we have switched to use of ceramics for our corals these past few months so no fresh concrete no enters any of our system tanks .... All 4 systems are now producing the best growth we have achieved since we started them up. Even some SPS variants I have had mixed success with to date now bursting into growth for the first time for us.
Pete
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Re: Concrete products and coral grow out.

Postby aquagrrl » Sun Dec 30, 2012 4:46 am

Hi Pete, I couldn't say one way or another as I've only had limited experience with concrete rocks and it was for a FO tank. However, the first thing that came to mind was PH. Are the rocks actually curing enough to not affect the PH and cause it to go too high? I know when I made rock it took way longer than I expected for the ph to go down. Several websites said it should take 2-3 months, but for me I had the rock sitting in fresh water for close to a year before the ph went down. Admittedly part of that was in the winter, but I'd say it was 6-8 months of non-frozen water before the ph came down.
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Re: Concrete products and coral grow out.

Postby Oceanarium » Sun Dec 30, 2012 6:00 am

PH is not the problem, I am aware of the increase that can be caused by rock that has not been sufficiently soaked I test this every week along with other parrams the rock never lead to any perceivable swings or excess.
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Re: Concrete products and coral grow out.

Postby Ben » Sun Dec 30, 2012 6:10 am

The problem with concrete is that it is never 100% the same in every mix unless you are collecting all the parts yourself washing them and mixing it yourself
Also as you probably know concrete is always going to be broken down by water as they want to become equal in density
Maybe something is breaking down in the concrete that corals dont like
I wouldnt use concrete in coral systems
I dont know much about clay / ceramic but if it has been fired in a kiln maybe it cant break down
Just my opinion
This is just my experience from the pool building industry
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