Water lillies and liners
 

I've had some water lillies in my fishpond for a couple of years now.
They had flowers on them when bought, but haven't flowered since - even
though they have grown nice and big. What do you do to get them to flower?

The pond started to leak so I've taken everything out to see if I can
re-seal it. It had a liner before, well bits of liner were still left,
and I'm not sure if the bituminous sealer will be the ideal solution.
Any suggestions as to what to look for in a pond liner? It is a pretty
small pond around a metre square and thirty centimetres deep.