A 12 gallon tank is not suitable for a Carpet Anemone. They require at least 30 gallons. The lighting (I'm assumming you have 24 watts, or 2 watts/gallon) is not sufficient either. Carpet anemones need high lighting, the same or even higher than what a Condy requires. If the Condy is not surviving in your current system, a Carpet will not either. Anemones are very difficult to maintain. If you want something similar,
torch corals or long
tentacle plate corals are great, if you don't have a clownfish that is.