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
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.
