In reality, it probably wouldn't. You've basically found a "bug"/exploit. Its not TA-specific, though. You can do it DA, also. Just wait for the AI to colonize a planet then hit it with a spore ship. I think that might be one of the reasons they upped the cost of the spore module in a recent patch

Well, I didnt know what to call it, hence the ""'s around the word "bug".

I suppose it would depend on how you look at it. Heavy gravity, for instance, would STILL be a heavy gravity planet even if you dropped spores on it. So if the Korath came along and bombed it, they would still need to know how to live in heavy gravity, or know the secret to surviving there.

Conversely, if the previous colonists had a tech that reduced the gravity inside a dome or some certain area, then yes, you could conquer it, and still have a functioning colony, assuming you didnt have to do anything maintanence-wise, etc. to sustain it.

I personally would recommend avoiding high gravity, toxic worlds entirely. They play havoc on your weight and diet regimen and the surgeon general says they are known to cause cancer and lead to birth defects...

Radioactive worlds, however, are perfectly safe.

(Also, what's with the +5% courage for aquatic colonization? Are you like, scared of water or something? Honestly of any colonization tech to have 'courage', I'd vote for Radioactive or Toxic. Probably radioactive given how much research I've done it, and it honestly scares the shit out of me watching these videos from Chernobyl)

i just find that using spore ships is simpler than using transports, i don't really care that it makes worlds toxic.

I don't see any logic gap here. Spore ships leave the infrastructure intact. The underwater cities or gravity generators or radiation shielding or whatthehellever the previous owners built to overcome the extreme conditions is still there, thus nullifying that environment. The toxic effect is the only one active after invasion, because previous environment + previous terraforming have cancelled each other out.

That assumes the previous owners had fully terraformed that world (ie, had the advanced tech for that environment). Sporing a world owned by someone with only the basic tech for that environment should only give 50% production -- the previous owners had only half terraformed it, so the same infrastructure shouldn't suddenly give the Korath 100% production. They should still have to have the appropriate advanced tech to upgrade that world from 50% to 100%.

That would be a good way to balance the current system in which the advanced toxic worlds tech effectively gives the Korath all the advanced techs, for invaded worlds if not for self-colonized ones.

I think it can be justified by saying that invading with troops, rather than sporing, will damage the terraforming infrastructure even if it doesn't destroy the factories and whatnot.

Maybe we need an Extreme Environment invasion tactic that doesn't give a soldiering bonus, but instead allows a successful invasion to keep whatever level of environmental adaptation the planet had under the old regime.

I've got a sort of backwards spore ship and environment tech question: If I've already researched Toxic Atmosphere Reductor, can a spore ship still destroy my colony, and if so, why?

I've played many games since spore ships came along, but I've never been hit by one in this context and never used them the couple of times I tried playing as Korath.

Swap invasion with culture flipping then. No troops destroying the infrastructure there.

And create a whol new problem: The spore module, now that it doesn't toxify the planet, is a game-breaker, because it just kills everyone and doesn't afftect the planet.  

Which doesn't fit the mantra of the Korath. The feed people's souls to the incinerator just to get factories...er slave pits to work better.

They get a technology that makes a planet toxic, but they know how to colonize such a planet...so what the heck do they care if they terraform the galaxy into toxic planets?