Hey man, welcome to Reef Central!! It's a great place for help.
I too have the 6g fluval edge up and running with 18w LED and two (very small) clowns with some coral. A few things you may already know:
1) Your clowns can't stay in that fluval forever. They will get too big.
2) If your tank is only a week old you need to be patient and wait. I didn't get any corals in my tank until like 8 months. I'm not saying that's what you MUST do... but really, they will need a more mature tank. Research the aquarium "cycle" if you're not already familiar with it.
3) I have thought long and hard about getting an anemone for the tank. I have decided that it's not a good idea. Most anemones can get pretty big, they need a good mature tank with consistent parameters...etc. What I was researching (even tonight) was good anemone substitutions that clowns host (although there is no guarantee your clowns would even host an anemone). What I came up with were (1) Long Polyp Leather, (2) Hairy Mushrooms, (3) Long Tentacled Toadstool, (4) Torch Coral, and (5) Frogspawn. If I were you (and in a lot of ways, I am you)...haha, I would look into a leather or a mushroom.
This small tank poses a lot of difficulties, but it really looks amazing in my opinion. Best advice is take it slow, enjoy the ride, and try to make your "pets" thrive, rather than just survive.
Good luck!