The short answer

Leafy lettuces yes — but iceberg only sparingly.

Why

Dark, leafy lettuces like romaine and red-leaf are safe, hydrating and fine to offer often. Iceberg lettuce isn't toxic, but it's almost all water with little nutrition, and too much can cause loose droppings.

How to feed it

Wash and offer romaine or leaf lettuce; use iceberg only as an occasional watery snack.

How much & how often

Leafy types can be frequent; iceberg only now and then.