So I've been playing the game for a while now, and after a few dozen playthroughs decided to dip my toes into Cravers. Read up on abilities: from the looks of it you need to be balancing planet depletion with approval by trying to keep the non-Craver population as high as possible, just have 1-2 Cravers per planet, and micromanaging them. Then I tried to play that way, and ran into a few issues:

- having more than 1-2 pop enslaved tanks your approval below the ground, and while you don't have rebel fleets spawning on you, the -75% to Food and Influence just kills off the entire population, and if you keep this up on too many planets, you'll just drop your entire empire into 0% approval hell

- the FIDSI benefit you get from slavery does not compensate for the -75% food penalty: the slaves just keep dying at a massive rate

- I am not sure if the Growth vats (did I get the name of the ability right?) ability affect only a single planet, or the entire empire, but it taking an entire turn is very expensive

So here's my question: how are you meant to use this ability effectively? Do you just go 0% approval empire wide, and compensate for the FDSI penalty with economies of scale? Do you send some slaves to the "core" worlds, and then use the newly conquered systems as approval fuel? Do you just ignore the entire system altogether, and keep Cravers and slaves separate (which is what I ended up doing, and felt extremely lame)? Is this only meant to be useful on very low populations? Early game only? Or am I missing something obvious here?

Thanks folks.

Well, it's all of it, really. You want to extract maximum resources while you can, and constant micromanagement is required for that. The trick to better balance is to have at least two minor population types in system. Do not boost Craver pop with luxuries unless you have 3 or 4 different minors present. That way Cravers will not grow faster then anyone else and will not deplete planets sooner, so it will be more manageable.

If there are too many Cravers in system - chain gang them. If you can't manage Approval because of Slave Drivers - throw minors into Feeding Pits (that's the name) to boost it. Keeping populations separately is also fine, as long as you are ready eat system up quickly and expand someplace else.

It can still be beneficial to have low approval, because Slave Drivers applies 250% FIDS on Craver pop (100% base + 150% from affinity), so you drop to 250 - 75 = 175% food production on Cravers, while still having 250% IDS.

I suggest to read this

The Cravers/Gameplay | Endless Space 2 Wiki | Fandom

The Cravers/Strategy | Endless Space 2 Wiki | Fandom

and this 

Steam Community :: Guide :: A Guide to Cravers (Updated)

for clarifications.