It's just something you have to try. boiling it does take out nutrients but it also makes it easier to digest. Try seaweed you can buy it in a grocery store some places. My haps and a few of my peacocks love it.
i slice and freeze cucumber, yellow squash and zucchini. when i want to give them some i just rubber band a few frozen pieces to a rock and drop it in.. they really love it.. and my pleco will eat the dark green skin on zucchini like nobody's business lol
i have tried the lettuce and seaweed, but my fish are just afraid of it moving around..