barola87, I agree with the others on lettuce, You can purchase the Red, Green or Brown seaweed from your LFS or you can buy Nori from your local grocery store (usually in the specialty Isle), Hermits, Snails and many fish will eat this.
However, you can use Fresh Frozen Peas or Fresh Frozen Broccoli thawed from your local grocery store along with the Nori/Seaweed.
Kaye