Are about to start my first aquaponic system, have read some books and watched a lot of youtube and dvd's.

But most of the information is about keeping (growing?) fish in Australia or America. I live in Sweden where e.g Tilapia is an exotic fish no one has heard of...

What type of fish do you recommend for my system?

The system will be indoors in my apartment and will be about 300-400 liters, kind of like this one:

I will focus on growing vegetables and would like the fish to be easy to keep and cheap to feed. Either with worms from my worm bin or with food scraps like bread, potato, peas...

The thing is I am currently unemployed and can't really afford going to the pet store and buying a bunch of gold fish and certainly not koi carp...

By the way, how many gold fish would you need to get a good yield in a system like the one in the picture?

One fish that is very common, and free, here where I live is the "European Perch" ("Abborre" in Swedish). http://en.wikipedia.org/wiki/European_perch
I've read about some people keeping them in their aquarium's but they seem to be very picky about what they eat and doesn't like temperature's over 20 degrees Celsius.

Would feel bad if I just went out and netted some and killed them in just a few days because I didn't know any better...