What fish are you feeding? My plecos and bristlenose simply adore zuchinni and peas. I do not cook it in any way. Just weight it down or clip it in one of those things with a suction cup made for the job . My clown loaches like it also.
u can give them sweet peas, lettuce (romaine preferable) zuchini, u can boil them if u prefer but that's just so the veggies sink to the bottom or u can weigh it down with something... what I do, I place a small amount of sweet peas (about 20 peas) in a small bowl with some water not much though, and heat it for 10 sec. in the microwave, let it cool down for a bit, squeeze the center out of the peas and feed it to the fish, sometimes I grab a knife and chop the outer shell of the peas so it will be soft enough for the fish to eat. they all enjoy it! ;D