I have played the game up to the point where you have to get to the flowers in the park but I can't figure out how to get past the little girl.
Spoiler
In your room in the very bottom left is a box.
I'm stuck, too:
Spoiler
Gave flower and ammonium to Alvin, still need algae and bleach.
I put a plastic bean in the filter but the tank won't get dirty, do I need to leave the room and come back several times or wait for a few minutes or what?
I think you may have to wait a little bit before the fish tank gets algae in it. You could also try unplugging the fish tank too. The bleach and ammonia are in the laundry room beside the kitchen. You will also need another item from the kitchen to collect them in.
algea
Spoiler
the algea has two solutions (both of which are mentioned) and one way give more points then the other.
I thought about doing a timer, but since I couldn't figure it out, i just made it so wandering around triggers it.
Leaving and entering the room a few times works too.
(sorry I didn't see this sooner)