The holes should be on any tube that can create a siphon, return and/or overflow.
If you haven't purchased a tank yet, do yourself a major favor, DON'T EVEN LOOK AT NON REEF READY TANKS. There is no reason whatsoever to even consider a non RR tank. If you have one already then you need to take the necessary precautions to prevent flooding and siphon breaks.
Be sure to purchase a sump large enough to handle any backflow from your main tank in a power outage. Many times standing in front of a running system and talking to the owner about it will help it all make sense. We have numerous members who would be willing to give a demonstration to you, I am one of them. Only thing is, I live a bit out of the area. If you'd like to check it out, LMK and we can work something out.
swimmer