Ponds and Water Gardens - Need to determine what new waterfall pump meets my needs

I want to purchase a new waterfall pump but am not sure what to buy. Can I get some advice? I have a wall that I have tiled and would like to have water cascade down at a low speed. we have built two holding ponds above and underneath the wall and the waterfall measures 9 feet wide and 10 feet high. We would like the water to "trickle" over the top edge. What kind of pump would work best and how do I control the water speed. We looked at the garden treasures waterfall pump # 59087 at Lowe's but are not sure if the pump speed can be controlled or if there is a better choice. Please advise, thanks.

Pumps are not variable speed. You need to control water flow with a valve in the pipe. Try to match the pump capacity in gal. per min. to your requirements.

Thanks for your help. that tells me what I need to know.