When I feed my 2 Foxface, one of which is 4.5 years old. I feed cheato, caulerpa, and nori. All of which supply them with what they need without any doubt. Bottom line is that feeding lettuce MIGHT be beneficial at best and harmful at worst and is totally unnecessary because better alternatives exist.There are vitamins to be had in the fluids of the lettuce. It should not be used as a replacement of anything, but just as an addition. My foxface didn't poop out anything that looked like lettuce, but again, that's not where my concern was. My concern is the vitamins that are absorbed while the fibrous mass passes through the gut.