i have had koralia nano's, and my friend has koralia 1's, based on those i'd say in a 29g go with koralia 2's. the nanos and ones just don't have the kick. i'd get 2 and stick them on the back wall, in each upper corner, blowing downish and toward the center. thats how i had the nanos running in my 29g, made a good flow pattern, but you will have to play with them when you get them to see what you like.