Potted plant watering system. (Involves water pumps.)

New problem:

On the pictures of the manifold the plastic pipe overlaps the black pieces quite well and is "crimped" with cable ties.

The pump, however, is a different story.

The pieces of pipe protruding from the pump are a little bit shorter and narrower in diamater.

As I am still testing the system - and it does work! - the length of the pipe from the manifold to the pump is unknown, and the inlet piece of pipe is "work in progress".

The problem is this:
I bought a couple of those hose clamp things which wrap around a pipe and are tightened with a screwdriver.

All well and good, but the gap from the pump's body to where the first ... "flange" thingy on the pipe is, is too narrow. The clamp is wider than that.

No big deal, I just tighten it a bit harder than I would like.

I'm guessing that cable ties may be the only ultimate way to go. Are there any other tricks to help with this problem?

Thanks in advance.