Is the purpose of the pump just to prevent stagnancy or will you be using a waterfall? If the waterfall comes into play, what is the head between where the pump will be and the output for the falls? I use a bigger pump (565 gph) for my pondlets ( five 35 gallon containers with spillways, total of 175 gal ) that flow from the bottom where the pump is to the top container. This produces a steady flow from the top pot down but certainly is not a disruption to lilies. I think the head on mine may be 18 to 24 inches because it travels uphill.

I have no fish, just lilies and parrot's feather.

I saw you other post too. I'm not sure that pump flow is really going to clean up your sludge issue, but some circulation is always good anyway. However as PK mentioned, lilies don't like a lot of disturbance. To control flow, you can always put in a splitter on the outflow side of your pump. Part of the water stays in the pond (perhaps directed toward the side) and part gets diverted to your fountain or falls or whatever.

I can't decide if I'm going to use the waterfall again or not. It gets soooooooo blackened with algae, and I don't want to use anything to keep it from happening. If I do use the waterfall, the top of it is probably only about 2' higher than the pump and maybe 5-6' from the pump. I may also just use some sort of spitter. But....what I meant about the water disruption to the lily is when I don't use the waterfall, I just use a simple tube that bubbles the water out and I set it so it's good, but anymore force might disturb the lily, since the pond is small.
Thanks PKponder!

Thanks chas....we must have been writing at the same time. That's a good idea about the splitter. That way, the water will be under and away from the lily. I will try that if I decide to return this pump for a higher gph one that doesn't have a flow control.

P.S. chas...........I've decided that my pond is cleaning up pretty good, in spite of the silt on the bottom.........so I might just leave it. I don't think that amount of silt can hurt much. I'm not into crystal-clear perfection. Having a reasonably healthy pond for the plants, frogs and snakes is good enough for me. Just found my 8th dead big green frog at the bottom for this season. I guess that's a wake-up call that I haven't been taking good enough care of it. I feel bad.....but I will change. I've always left "stuff" in the pond in late Fall, thinking it's good cover for the frogs/tadpoles, but the decomposition no doubt isn't good at all for them.......especially if I don't aerate it for months at a time.