sera guide - Marine aquariums

33 Coarse coral sand is excellently suitable for the marine water aquarium. It is decorative and contributes to pH value stabilization due to its lime contents. However, some fish species (e.g. gobies) by all means require a zone with sandy bottom material into which they can retreat during the night. A separate zone with fine coral sand must be arranged at the bottom for these animals. The remaining bottom area is covered with an approx. 3 cm (1.2 in.) thick layer of coarse coral sand. It is advisable to separate the dif- ferent kinds of bottom material from each other with stones as to prevent them mixing up. Coral sand of different grain sizes is avail- able from your local specialized retailer. Another important bottom ground task is to provide additional settling space for the bac- teria that require oxygen (aerobic) in the up- per zones and for the bacteria living without oxygen (anaerobic) in the lower zones. These purification bacteria in sera marin bio reef- clear break down pollutants as in the filter. The dry coral sand must first be washed thor- oughly. Put it into a clean bucket in portions, and pour about 4 – 5 liters (1 – 1.3 US gal.) of warm tap water on top of it. Stir the sand with thorough, circulating hand movements, then pour away the water along with the pol- lution. Repeat this procedure until the sand appears clean. Now fill the sand into the still empty aquarium. 6.1 Bottom gravel 6. Setup