The Heteractis crispa (long tentacle, LTA, Sebae anemone) is actually one of the more difficult to keep. They do prefer to be in the sand or lower in the rock work with a moderate current, so the very high lighting of a 400W Metal Halide would be needed for the optimum health of the anemone. These anemones can grow up to 18 inches in diameter and have tentacles 5-6 inches long so they will need a lot of space around them to full expand.
Another species that is often referred to as a Long Tentacle Anemone is the Macrodactyla doreensis (LTA, Long Tentacle, or Corkscrew). This anemone should only be placed in the sand with a moderate and will also need the very high lighting of a 400W Metal Halide to reach the 30" depth to keep it at optimum health.
Both of these anemones will require frequent water changes and excellent water chemistry at all times to maintain optimum health. Keeping either of these will require very vigilant measurements of tank parameters and ensuring they do not change by a significant amount at any time. These anemones can live 100+ years in nature and unless you are willing to really dedicate to the maintenance of the tank and the cost of setting up a proper environment for them they may only live 6 months to a year.
One thing to note if you do plan to have clowns hosting in either of these Anemones be sure to choose carefully as perculas are not natural symbionts to either of these anemone species.