If you are a beginner, there are a few choices that you might want to consider. Some of the most commonly kept types of anemones in the aquarium trade other than Heteractis magnifica are the Carpet Anemones identified by its scientific name of Stichodactyla haddoni. Although the species can be more tolerant towards a less ideal condition in the tank compared to the H. magnifica which can be extremely demanding, the carpet anemones still need as much attention from the aquarist especially on the lighting. Appearance wise, some of it are blue, purple or green in color and overall; S. haddoni is slightly different from the usual protruding sea of tentacles like the H. magnifica. Nevertheless they still belong to the anemone group and become an automatic choice for beginners due to their hardy nature that can adapt and survive quite well in captivity. As implied by the name given to them, the flat, carpet-like creature can always be found clinging to the aquarium live rocks surfaces. Other examples I would recommend one to consider are the Rock Anemone identified by its scientific name of Epicystic crucifer and Bubble Tip (Bulb Tentacle) Anemone also called Entacmaea quadricolor. Just like the S. haddoni, both species are also the hardy types that make excellent addition to your saltwater tank clownfish collection.
A good aquarium practice when keeping anemone is also about choosing the right tankmates. Sometimes selection of other invertebrates like sea fans can cause harm and attack your anemones and threaten their survival. Introduction of different species even though they are closely related, will still need careful consideration as not all anemones types are compatible with each other. Even your aquarium fish can become the culprit and the most notorious is the presence of certain species of butterflyfish and especially puffers which will outright hunt them and will practically destroy every sea anemone creature that they could find. With that being said, at times instead of becoming the subject of bullying, certain species of anemones can turn aggressive, to the extent of killing other invertebrates or even fish species. Unwary Acanthuridae like the unicornfish, tang fish can often fall prey and so does the clams and starfishes sharing the same reef home. My advice is to avoid the community approach as this always involves trial and error to find out the most compatible mix, thus it would be best to confine your anemone presence only with clownfishes. As mentioned earlier, one of the key things to ensure their survival is to make sure that water movement is vigorous to remove the accumulated waste but the same objective can also be achieved by introducing a host of cleaner shrimps or small hermit crabs. Other hobbyists go to the extent of using liquid nutrients specially prepared for anemones to provide the extra boost and keep their pets alive. Most of these can be bought at the local fish shop, but avoid buying on instinct. Make sure that the most important thing is to check with the sales person on what and how these can help. Focus on the iodine based reef supplements.