Boiling the veggies for that length of time nullifies much of the nutritional benefits--some will argue the boiling them for anything length of time will do this. The reason to feed veggies is the increased number of fresh vitamins. Most vitamins are sentive to extremes in temperature, so the good stuff either breaks down, or is released into the water.
Instead, just throw them in raw. The fish will eat them, even if they float.