@ Thaago: At the time, I was sort of living from paycheck to paycheck. I could not afford a battlestation, and by the time I find about invasion fleets, it is too late to build battlestation. I think they take 60 days to build, and invasion fleets arrive in about 40 to 50 days (my first colony was near the core worlds). I had about 200K credits to spend, but I can easily burn that up resupplying and refueling my midgame fleet. Also, do you need blueprints to arm battlestations properly? At the time, my blueprint options were very limited.
It was only after I took max colony skills and repelled my first two invasion fleets that things began to snowball in my favor. It took a long time before I got a third invasion fleet, and by then, I was well prepared to tear them up.
As for colony growth freeze, I discovered to just remove spaceport from time to time, then rebuild it after population falls low enough. It is too late if you let it hit size 4, unless negative growth can downgrade colony size.