150g tank is one of the deeper standard sized tanks. I question the amount of lighting you have to be able to support 2 carpets. 5 fish at one time is frowned upon because that is a very large increase in bioload for your tank (especially one that's only been running for 4 months). Heck, my tank has been up for a year and a half now... and I still haven't added 5 fish total, never mind 5 all at once. Another thing to think about: if the clowns pair off, and each pair takes 1 carpet, then you'll have 1 clown with no mate or carpet (I believe that if you are going to have a pet-yes, even fish-you owe it to the pet to keep them happy. Keeping them alive isn't enough) If you're that interested in doing the carpet/clown thing, buy 1 carpet and 2 clowns to get started... doesn't make sense to dive right in with 2 carpets before you know if the anemone will be happy in your tank.
patience is the key, and it sounds like you might be rushing a little. Just my $.02