Yota does not understand why you keep so much surpluss food production?
My tactic is: specialization.
Included all my colonies one turn before I conquer the last enemy planet with my space marins (=D).
I do as following:
Terra- and Gaiaplanets are used
soly for food production. If I have more farmers than I need (food surplus) everyone who is not needed goes to research.
Importent buildings for such planets are soil enrichment and weather control (I dont think you have that one yet).
After that maybe an automated factory for some trade goods and some research buildings. But those are really second priority.
The mineral category is absolutly unimportant, as you build only the nessesary buildings here.
Rich and ultra-rich planets
allways become industrial planets, because honestly as you would say, that's what they are for. So they obviously get all the industry and anti-polution related buildings and some reasearch facillities for good meassure (for phases where you dont want to build more ships, and all buildings are build. Also they generate some RP on their own, even without scientist).
Even if they are terra class planets. No farmers.
Everything foodrelated gets shiped around on freigters. (There are some disadvantages to this, as an enemy fleed in the system cuts the planets from the food supply system, but you make the best out of every planet this way.)
After the industry is up, those planets become your shipyards. They churn out your average battleship in ~10 turns.
Every other planet gets used as a research planet. Remember the ice-planet from Mass Effect 1? Just like that.
Every research building, again no farmers (because, if a farmer would make more than 1 food, you would use the planet as a farming planet, right?)
And a bunch of industry buildings. Those in fact never hurt anyone, but keep focused on the role you want the planet to take.