Marine Aquarium Substrate: CaribSea Seaflor Special Grade Reef Sand

Aquarium Substrate for marine and reef aquariums from , Seachem,  and Brightwell Aquatics.
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Generally the favored substrate of today's modern reef aquariums, many feel that sand gives the marine aquarium a much more natural look. Additionally, the sand bed provides a place for the growth of micro-fauna and bacteria which aid in the biological filtering of the marine aquarium. Sand is used to cover the bottom of the aquarium to various depths and now is available in a variety of colors (from pink to black), size (very fine "sugar sand" to large grains) and name brands. It is generally recommended to use aragonite sand, so that it, like the CC can bread down slowly over time adding calcium carbonate to the water and helping to buffer pH. Silicate-based sand (usually referred to as play sand) should be avoided; it compacts readily, creating a concrete-like substrate and releases silicates into the water which can cause diatom blooms. Properly setting up any sand bed requires the introduction of bacteria and micro-fauna through the introduction of true Live Sand (not the bagged stuff purchased off the shelves from your LFS which at best contains only bacteria). Some of the disadvantages of a sand bed include sandstorms in the event of too strong of a current within the aquarium and sand being dropped onto LPS polyps. A sand bed is required to properly maintain certain species of fish and invertebrates, however care should be taken in the selection of livestock for the marine aquarium with a sand bed. Some critters, such as Diamond Watchmen gobies and sand-sifting sea stars, can quickly consume all the micro-fauna and bacteria in the sand bed in a smaller tank, thus causing the sand bed to become inert and no longer function for biological filtration. Once they have consumed all the micro-fauna, these animals will often slowly starve.
There are several different ways to use sand as amarine aquarium substrate, but I'll focus on the few most commonways.
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Now, if I could put a side bar within a side bar, I'd discuss different commercial sources for substrate of different grain sizes and compositions. Instead I'll just note here that there are places outside of your local aquarium store or pet store where you can find cheap substrate suitable for marine aquariums. In addition to browsing your local aquarium store's substrate selection, don't hesitate to venture into a hardware store and/or construction supply store. However, do be sure you know what you're getting and what you're putting in your aquarium (potential contaminates and all). Lemkemeyer, Jurgen. The Substrate (In the Marine Sector,too...). Today's Aquarium-Aquarium Heute 1/87.
Photo provided by FlickrMarine Reef Aquarium Substrates: CaribSea Arag-Alive
Photo provided by FlickrSubstrate for Saltwater Aquariums - Marine Depot
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This is another form of calcium carbonate, somewhat softer than dolomite, yet not much. It begins to dissolve between a pH of 7.2 to 7.6 (metastable range), and can be considered a very suitable substrate for undergravel filter systems, yet of little value where some calcium buffering would be helpful. Calcite products, generally mined and crushed limestone from ancient reef deposits (see crushed coral above) are ineffective buffers in marine aquariums. As with crushed coral, there are choices. Crushed oyster shell, mostly calcite, is just that and is sold both at feed stores as chicken feed, and in some pet shops as substrate for marine aquariums. It usually contains a lot of calcareous dust and therefore requires a thorough washing before use. Even though two or three washings may fail to remove all the milky white calcareous dust attached to the shell particles, it’s safe to use. However, this material is ‘flat’ pieces of shell and may pack tightly over a period of time thereby restricting diffusion. Additionally, oyster shell pieces have smooth surfaces, making it difficult for bacteria to adhere, and the larger the particle the less total surface area in a given volume when compared to small sand grains for bacteria to adhere to.