What type/size aquarium does my leopard frog need to be comfortable and not drown his self?

I have a leopard frog tadpole and was wondering what size aquarium he needs and what type of decor and rocks do they like? I have read that as adults if hey are bored they will drown there selves, is that true? If you know of any websites or have any tips please let me know. Also how often should i feed it as a tadpole and frog? what should he be eating? i gave him some boiled lettuce last night.

Here are a few sites. I like the first one the most.