The temperature

Sea is a very big space and so the unimaginable amount of water is the reason why there are such stable conditions. Of course in every part of the world there are a bit different conditions. In closed seas the salinity is higher than in the open seas because there is an intensive water evaporation and the water is renewing a little slower. A good example is the Dead Sea. Another reason why this sea has so high salinity is the fact that there are more minerals than usual. The temperature is different too. Of course at the North Sea the temperatures are different than in the waters nearby the Equator. But if we speak only about the tropical seas, there is difference only a few °C. As it's mentioned above, the stable conditions in tanks are important because just like in the freshwater tanks also here could the bad water conditions cause stress and the stress causes illnesses. The temperature is one of the most important things in general. It should be about 24°C. Here it is so easy to show you that the size of aquarium is so important. Because the bigger the tank is, the more stable the temperature is, even if there is an electricity outage. Big amount of water is capable to keep the warm for a while. However, not longer than for a one day. You can even stabilize the temperature for unpredictable cases; if you have an isolation material on the back, on the sides, under the tank and maybe within the aquarium cover too. It is enough to have a clear glass only at the face of the tank.