The thing with perennials, and most plants, is giving them time to grow and develop.  Think two years for perennials, in most cases, and 3 for plants.  By this time, you can see a direction and expansiveness.  By planting further apart, one may feel empty briefly, say for the first year, yet, part of all gardening love regards growth and development as an essential aspect.  It is patience that gardening teaches us, lol. Incidentally, the piping was left like this for purposes of this picture.  We have since raised the height of the waterfall, thus its temporary look.