Population limits clarification

[ruppert29]

My homeworld has a population limit of 11. All the rest of my worlds have pop limits of 3, even my class 16 worlds. A couple of these worlds are 3/3 with a red exclamation point after them. Tooltip does not explain what that means, probably that it can't grow pop(?). Is the only way to get there pop higher is to create cities which then sends you into a approval decline eventually. My homeworld at 8.4/11 is hinting at that. I do create a colony periodically. Should i be migrating pop until all my planets are 3/3 (is that wise?)? What else should i consider? Is 3/3 bad?

[Jamite]

build cities! it'll increase your population. However once you do it'll be permenent. So choose wisely where you build a city.

[jonnin]

moving them around helps in the very early game, but mostly that should happen naturally by making colony ships.
if your approval drops, make something to increase it. large populations are trouble if you don't up approval, but small population worlds output much lower levels of science, production, etc.
its a balancing act, as is much of the game.

[blackphoenixx]

Your homeworld has a higher capacity because your capital gives +10 pop while normal colony capitals only give 3.
The red exclamation mark simply means that the current limit is reached and your population can't grow anymore.

To get more population capacity aside from cities you can upgrade the colony capital twice for +1 each. Some resources (Monsantium iirc) also increase population capacity, as does the Bernal Sphere precursor artifact.

Also cities give a 10% population cap increase per level of adjacency so you should never need to build more than one on all but the biggest planets if you take advantage of that. Which is a good thing since cities consume food.
Much easier to put a hospital, farm or food distribution (or all three) next to one and raise population capacity that way instead of building a second or third city. Some approval buildings give population adjacency too.