thanks for getting back to me.
re: flow -30 GPM would be sufficient. could probably be less. the pump could be submergable or surface. the application is a modified aquaponic system in Latin American rainforest to provide food to the indigenous. i am a director of a humanitarian group (www.deadwheat.com) based in Panama that develops contextually appropriate technologies for water, food (e.g. aquaponics) and clean air security needs among those living in the rainforest belt. in a nutshell, we construct an aquaponic system on hillsides curving out 2 degree slopes into the hillside for growbeds that zig-zag back and forth and drain into each other and eventually a Tilapia pond. we need to circulate water from the pond (low point) to the highest growbed (i.e. 8' head). we can take our time flushing water through the system, so we don't need a high GPM capacity. we just need to be able to achieve the 8' head.