Fish tips please. semi aggressive tropical?

Cycling the tank has to start with an ammonia source (fish, fish food, old filter media from an established tank, or pure ammonia which is hard to find). Your tank was left a week with water, but the cycle didn't start. That's why the water tested fine. You've got to start the cycle and then test the water for ammonia daily and do water changes as needed. Then go through the rest of the cycle lightly stocked until its complete. You also bought fish that have too much bio load for a 20 gallon tank. Try something tiny like small tetras or guppies.