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There are 2 ways to create new colonies:

  • If there's an unoccupied planet in a system where you already have a colony, your colony can build a Colony Base (200 PP).
  • Otherwise you have to build a much more expensive Colony Ship (500 PP). You may even build a Colony Ship for a planet in a system you already occupy if there's a good reason for wanting to found the new colony faster than your colony in that system can build a Colony Base, for example if the planet has gem deposits.

In the early game even a Colony Base is a significant construction project, so you need to decide what you hope to gain from each colony, and whether the gain justifies the cost - it might be better to concentrate on something else, such as research or on growing the population of your existing colonies or on improving their population capacity, research or industrial capabilities, profitability or, if your race is not Lithovore, their fertility.

This is quite complicated because:

  • A few planets have special features that make them unusually desirable, even if you wouldn't want a similar planet without the special feature.
  • Some racial traits affect the desirability of planets. For example a Medium Ocean planet has an initial maximum population of 4 for a "standard" race, but a maximum of 16 for an Aquatic race, which also gets a farming bonus there.
  • Most planets can be terraformed when you get the technology (it's the only one at that level, so even an Uncreative race can research Terraforming if it wants to). So you may want to consider how easily a planet can be terraformed into a "good" planet for your race; and how to use it in the meantime.

Good players know all the possibilities and do this analysis without conscious thought. If you're a newcomer to MOO II, don't get discouraged by the apparent complexity of all this - after 10-20 games you won't notice yourself thinking it all out.

At some point you will have to stop colonizing anyway, for example because it would be difficult to defend new colonies far away from established colonies that could build warships to protect them.

This page only deals with colonization in the early, low-tech stage of the game. Later you should generally "colonize" by invading other empires' colonies. In this mid-game stage there may be a few uncolonized planets behind the expanding boundary of your empire, and you may wish to colonize more "difficult" planets because you now have technology and money to make them useful in a reasonable period of time. But this guide cannot anticipate how the mid-game will develop, especially which technologies you will research at this stage.

Planets without special features[edit]


Population is power. So ideally you want mainly planets that have a large maximum population or can easily be terraformed to a large maximum population. But the maximum population partly depends on your race design - Subterranean and Tolerant races get higher than normal maximum populations on all planets; Aquatic races get higher than normal maximum populations on "wet" planets. Fortunately the game software helps by showing a planet's maximum population when you run your mouse over the planet's icon in various screens:

  • If the planet is empty, it shows the maximum if colonized by your race.
  • Otherwise it shows the maximum for the race that currently occupies it.

Minimum useful sizes[edit]

Usually it's not worth colonizing planets whose initial maximum population for your race is less than 4:

  • In the early game you're short of cash - even if you've chosen a race design with advantages in money, e.g. with a Democratic government, because cash races are usually not strong producers and have to use the "buy when half-built" technique a lot.
  • To help pay for the maintenance of buildings on the planet, you'll generally want to build a Spaceport. But on planets with normal maintenance costs Spaceports only make a profit if the population is at least 4; and on Toxic, Radiated and Desert planets maintenance costs are higher, so the break-even population for a Spaceport is higher.
  • When you build Biospheres at a colony, its maximum population will increase by 2. But Biospheres have a maintenance cost of 1 BC per turn. Ideally you should build a Spaceport before Biospheres, to pay for the Biospheres.

Size affects pollution[edit]

A planet's size also affects how fast it can build, because pollution starts to bite at lower production levels on smaller planets (Tiny - 2 / Small - 4 / Medium - 6 / Large - 8 / Huge - 10; buildings/leaders/research that reduce pollution increase this number proportionally).

Population 1 housing colonies[edit]

There's one important exception to all of this: if you have a few planets with maximum populations of 8 or more (for your race), you could colonize a smaller planet to use it as a Population 1 housing colony. The smaller planet should ideally be one that can easily be terraformed to a useful size later.


Food production is not a constraint for Lithovores in the early game, but even they should try to colonize planets that are good for farming, so that they can later support non-Lithovore populations that they have conquered.

Depending on the type of planet, your colonists can produce 0, 1, 2 or 3 food per farmer – if your empire has no food bonus and before you implement food-boosting technologies, 3 is possible only for Aquatics on "wet" planets and for non-Aquatics on the very rare Gaia planets). Non-Lithovores would obviously prefer to colonise planets where each farmer can produce 2 or 3 food in the early game - once again this depends on your race design: Unification governments and, on "wet" planets, Aquatic races can produce more food. Colonizing a lot of planets that need to import food will harm your economy in a number of ways, whose combined effect is serious in the early game:

  • Your better planets need to do more farming, which diverts colonists form research and production.
  • You have to build more Freighters, when you'd probably prefer to build something else or to stockpile production.
  • Each Freighter costs 0.5 BC per turn that it is in use.

Low-fertility planets should generally be used only as Population 1 housing colonies - preferably sending people to other colonies in the same system, to avoid the costs of using Freighters.

If you have a choice of 2 low-fertility planets, colonize the one that will terraform directly to to a reasonably fertile planet (for your race) later.

Mineral wealth[edit]

Rich and Ultra-rich planets[edit]

Naturally you'd prefer to colonize the richest planets, because:

  • They can build faster, or can build at the same rate with fewer workers, so that you can have more researchers or farmers.
  • Richer worlds suffer less from pollution than poorer worlds of the same size.


  • The best rich planets are almost always guarded by space monsters.
  • The rest are usually no-farming planets.
  • And most of the rest have either small maximum populations (a double whammy, as small size also make pollution bite at lower production levels) or high gravity (which reduces productivity by 50%, see below).

Rich or Ultra-rich planets with a maximum population of 1 for your race are useless, since their populations cannot grow and therefore you can't use them as Population 1 housing colonies. No-farming but larger Rich or Ultra-rich planets make very effective Population 1 housing colonies provided they are not crippled by higher gravity than your race is comfortable with - Housing colonies' population growth rates are determined by their production, which is increased on Rich or Ultra-rich planets.

Poor planets[edit]

Poor planets with high maximum populations can be valuable assets - they're of little use for building ships, but can make significant contributions to your cash and to your research and/or farming.

But if your race is not Lithovore:

  • You should think carefully about colonizing Poor planets where your race can produce only 1 food per farmer, as these planets will take a long time to build Soil Enrichment and therefore a long time to contribute to your research or food supply, because they will struggle to feed their own populations.
  • Usually you should not colonize poor Barren or Radiated planets, as their poor production will make them inefficient as Population 1 housing colonies and will make them take a long time to terraform later.

Generally you should not colonize Poor planets that are Small or Tiny - small size and poor minerals both make pollution bite at lower production levels.

Ultra-poor planets[edit]

Avoid them! Especially as most have the additional handicap of low gravity, which reduces the productivity or most races by a further 25%.

High-maintenance planets[edit]

Buildings on Desert and Radiated planets have maintenance costs 25% higher than normal, and those on Toxic planets have 50% higher maintenance costs than normal. You should still colonize these planets if you need to hold the system for strategic reasons, the planet is large, you have a good extra income or if they have good enough bonuses.

It may still be useful to colonize Desert planets with maximum populations of 4 or more:

  • These are large enough for a Spaceport to make a profit at a population of 5, although you may have to build Biospheres first in order to increase the population.
  • Desert planets terraform directly to Arid, which is one of the largest increases in maximum population.

Radiated planets cannot be terraformed until Radiation Shields have been built, then they are converted to Barren worlds by building the shield. For non-Creative races, researching Radiation Shields means forgoing Class 3 Shields, the first decent space combat shields. And then they terraform to Desert or Tundra. Desert never gives a higher maximum population; Tundra is no better for most races, but excellent for Aquatic races — it provides the same population capacity and farming productivity as a Terran planet provides for non-Aquatics.

Most races should avoid colonizing Radiated planets early in the game unless the planets offer some specific advantage. There are 2 main exceptions:

  • You could use one as a Population 1 Housing colony if there are high-capacity planets in the same system.
  • If the Radiated planet is rich and the others are not, the quickest way to produce the additional Colony bases is to colonize the Rich Radiated planet first. This assumes that you would not want to build more than 1 Colony ship for the same system, which is usually true in the early game.

Most races should avoid Toxic planets except possibly where they have special benefits. In addition to the high maintenance costs, Toxic planets cannot be terraformed. Usually only Tolerant Lithovores can get any benefit from them, and even they suffer from the higher maintenance costs.

Planets with special features[edit]

Those that have special features and no disadvantages are almost always guarded by Space Monsters. This section covers how best to use those that have disadvantages.

Gold and gems[edit]

A planet with gold deposits produces a "special income" of a flat 5 BC per turn in addition to the normal tax revenue from its colonists; gem deposits are even better, producing a "special income" of a flat 10 BC per turn.

However you need to think carefully about colonizing those that have a maximum population of less than 4 for your race. If you use a Colony Base (200 PP), you could have used the same production effort to produce 100 BC, so the gems alone will take 10 turns to repay the investment, and the Colony Base was most likely produced by a new colony that could have done other things to improve its own contribution to your empire. If you used a Colony Ship (500 PP), it will take 25 turns to repay the cost. If the first colonist makes Trade goods, that adds about a further 1 BC per turn, reducing the payback period by 10%.

Of course the financial return is not the only reason for colonising planets. But if a planet will never contribute significantly to your empire's production or research or farming, money alone is not a good reason for colonising.


A few planets have Natives, who don't pay tax, can't be moved to other planets and can do nothing except farming - which they do far better than any race you can design — a Unification + Aquatic race on a "wet" planet is the only one that gets fairly close. Natives come in sets of 3, so planets with Natives have to be least of Medium size, otherwise races with "normal" population limits could not colonize them. Most planets with Natives have a disavantage - Desert (+25% maintenance), Poor or High-G.

Even so, you should colonize them as soon as possible, even if your race is Lithovore:

  • Lithovores will eventually need to feed captured non-Lithovore colonies.
  • Natives produce a food surplus of at least 6 (on a Desert planet with no improvements), which would be worth 3 BC per turn to a Lithovore's treasury.
  • Other races can take the cash benefit or use the Natives to feed their people, freeing other colonists for production or research.

To decide how and when to develop colonies with Natives, imagine that you have a colony with X-3 colonists:

  • If only 1 colonist excluding the Natives, it's useless to build Housing. You could stockpile production for terraforming when you discover it, or order the colony to produce Trade Goods for more cash.
  • If there's room for 4 colonists excluding Natives, develop the planet normally. That way you get the production and/or research from the colonists, and a few spare food that will feed colonists elsewhere or increase your income a little.


A few planets have artifacts left by long-departed advanced civilizations. The first empire to visit the system gets 1 or occasionally 2 free technologies (this benefit is greatest for non-Creatives) and colonies there get a significant boost in research productivity (+2 per scientist).

Artifacts planets are never no-farming planets but some are Desert (+25% maintenance costs). Sometimes it's best to take the free technologies and leave the planets uncolonized. The effort required to build a Colony Base or Colony Ship in the early game will divert resources away from research at other colonies, and this is unlikely to be a good investment if the planet initially cannot support 2 scientists plus 2 workers, before Biospheres or terraforming - that's probably the minimum because it assumes that the planet will import all its food, which costs 0.5 BC per unit of food (i.e. per Freighter load) and will divert colonists at other colonies into farming, probably from research. This is fairly complex, as it depends on your race design - Lithovores won't worry about food; Tolerant, Subterranean and, if the planet is "wet", Aquatic races can produce useful populations on Small planets.

Many Artifacts planets that are not guarded by Space Monsters are poor, but that is not a serious drawback, since Poor planets are often good places to do your research and the presence of Artifacts is a bonus.

It may just be worth colonizing an Ultra-poor Artifacts planet provided it will support 3 or more researchers plus 2 workers without needing to import food - an Ultra-poor colony will have to "buy when half-built" almost everything, so you need to avoid the additional cost of importing food. If you colonize an Ultra-poor Artifacts planet, maximize the research and cash benefits by sending in colonists from separate Housing colonies - an Ultra-poor colony needs to use all its meager production for construction buildings and cannot afford to build its own Housing.