Anemones are in a class known as Anthozoa, this also includes corals.
Most anemones are considered sessile, which means that they basically attach themselves to a rock, glass, or substrate by their "foot".
Anemones have two layers of cells, and each has a specialization for different functions, the outer layer is masked by something called nematocysts, which allows the anemone to sting, this layer also consists of muscle.
The inner layer of the anemone consists of a simplified digestive system which allows the anemone to eat food that is captured by its tentacles.
In nature,Anemones are predators, and are capable of consuming numbers types of food which are not limited to crabs, small fish and urchins.
Most Anemones require moderate to intense lighting, because they contain zooxanthellae, which are a photosynthetic organism, which gives the anemone nourishment through its waste.
Anemones do not need to rely on target feeding in order to survive.
The size and shape of an Anemone will change based on the nutrients that are available in the tank.
When keeping an Anemone in your aquarium, you should have covers over all intake pumps and power heads.
Anemones will move, and there have been a lot that have lost the battle to and intake pipe, power head, or overflow drains.
This is a very important thing to consider when keeping an Anemone.
The best way in order to combat the problem of anemones demise is to place a foam material or cartridge over the intake pipe, this will help by making the water suction being over a larger area.
Another very important thing while keeping anemones is to be careful of your heater, and if possible make your heater be housed in a sump where the anemone does not have access to it, If the Anemone decides to attach to the heater and turns on, the anemones foot will be burned, which usually ends in a fatality to you Anemone.