and adjusted with test kits and frequent manual dosing of calcium and pH buffer additives requiring no additional equipment. Alternatively, automated methods employing small dedicated computers with electronic water quality monitoring capabilities are often used to control water chemistry parameters via several components including calcium reactors and kalkwasser reactors. Calcium reactors are canisters filled with crushed coral skeletons. Carbon dioxide is injected into the canister acidifying the water and dissolving the coral skeletons. The acidified and CaCO3 rich solution is then pumped into the sump. The excess CO2 then diffuses out of the water and into the air leaving behind the CaCO3. Kalkwasser is an aqueous solution of calcium hydroxide, Ca(OH)2. The kalk reactor stirs and dispenses the solution into the sump where the Ca(OH)2 combines with dissolved CO2 to produce CaCO3. These components must be controlled by a computer to prevent dangerous changes in pH due to the acidic calcium reactor effluent or alkaline kalkwasser effluent. Optimal water parameters are: Salinity: 1.022–1.025 sg or 30–34 parts per thousand (ppt) Temperature: 24–27 °C (76–80 °F) Ammonia (NH3): 0 parts per million (ppm) Nitrite (NO2−): 0 ppm Nitrate (NO3−): 0–10 ppm Phosphate (PO43−): 0–0.06 ppm pH: 8.2–8.6 Calcium (Ca2+): 400–450 ppm Alkalinity: 7–12 dKH Trace elements can become depleted by marine livestock and filtration, and can be replenished during a water change. Safety Large volumes of electrically conductive salt water, complex plumbing, and numerous electrical appliances housed in close proximity certainly pose a significant risk of damage to both person and property and require close attention to safety. All equipment should be used according to manufacturer instructions. Electrical equipment should be placed above water level whenever possible, and drip loops should always be used. Circuit limits should never be exceeded and all appliances should be plugged into ground fault circuit interrupter (GFCI) outlets. These can be purchased at any hardware store and are relatively easy to install. Plug in GFCI power strips are also readily available. Home monitoring equipment with water sensors can also be adapted for the home aquarist and used to alert the owner of power outages or water overflows. This equipment can allow for timely intervention in a potential disaster and provides an added sense of security for frequent travelers. Nano reefs A nano reef is a type of marine aquarium that is typically less than 140 litres (30 Imperial gallons / 37 US gallons). The exact limit