Simply Koi and More Koi

Hi, I have just built a new pond and have changed from pump fed to bottom drain/gravity fed - which is brilliant.
My question is simply is there an easy way to automatically maintain the water level in the pond by using some sort of ball valve system? There isn't room to put one in the filter so I was wondering if anyone has developed a method of fixing one to the side of the pond? My new pond has a rubber box liner so I couldn't glue or screw into it.

Hi,

Its best to try to keep as much out of the pond as you can so that the fish don't bang into them especially an auto top up as it could end up flooding the pond.

You can get some fairly small units that will fit in most filters and if you do go this was it would be a good idea to install a overflow as well.