Why do paddling pools turn green and how do you stop them doing so ...

[Twiglett]

that's it really

Change the water

The water turns green cause there is algae growing in it

We let the water out everytime dd uses it and put it in the shed (still blown up)

As crazy as it sounds, bleach (which is what chlorine is). We have a very large inflatable pool which we fill once a year and my dh adds bleach to it to stop it turning green, I have no idea how much you add and would not advise you doing this without further advce. We were told to do this by a pool company.