Will the strainer and main tube for the Tetra Whisper 60 gall. fit in my 29 gallon aquarium?

If the strainer tube is too long then just cut it down so that it will be just above the bottom of the tank. As long as you do not have small or weak fish they should not get sucked to the strainer, if so then put sponge over the strainer. As far as feeding goes then just unplug it while you feed so that the food does not get sucked into the filter. It is good to have a filter that is bigger than what you think that you need.