Aiptasia Anemones: How to control them, so they don't take over your saltwater aquarium?
As you've already suspected, there is no perfect answer, however you can approach the problem in two different ways. Read more and see video below. ↓
The first approach of Aiptasia management - A chemical approach:
Various manufacturers have developed various products to eliminate Aiptasia that hobbyists have reported being successful in using. The simplest and most popular method is mixing two parts of water to one part of kalwasser (Calcium Hydroxide). Place this paste in a large bore syringe and place a smudge of the paste right in the mouth of the Aiptasia. A reminder that the paste is highly caustic, so care must be taken in handling this mixture. Within minutes of ingestion of the paste, the Aiptasia will begin to dissolve and can be removed with a small bore siphon. Aiptasia Removal products such as Red Sea Aiptasia-X and Joe's Juice will also work if you don't want to mix your own paste.
The second approach of Aiptasia management - A natural approach:
Three different species of marine animals including one fish, one shrimp, and one Nudibranch have been successfully used as natural control for Aiptasia. The Copperband Butterfly (Chelmon rostratus) is known to eagerly devour Aiptasia, the Peppermint shrimp (Lysmata wurdemanni) will also eagerly devour Aiptasia and will feed on flake food, making them an excellent choice for hobbyists of all levels. The newest found predator and perhaps the one with the best potential is the Nudibranch species (Berghia verrucicornis). The major drawback for these Nudibranchs is that they will eat Aiptasia, but nothing else. After the Aiptasia have been eaten back there may be so few of them that the Nudibranchs has trouble finding them, and can eventually starve to death. One suggested alternative to having these Nudibranch starve to death is passing the Nudibranch from hobbyist to hobbyist tanks (this method works well in organized Marine Aquarium Clubs) or have a small 10 gallon tank set-up and culture Aiptasia to feed the Nudibranchs.