we manufacture plastic ponds on site, have a big range, check out Gardenpools.co.nz (new website up soon i think) as well as stocking a heap of stuf from stone and water world
you really need 75L per fish minimum and around 30-40cm deep so around 300L would be ok for 2-3 fish max but take into account the pump size and planting container size you're pushing the comfort levels.
a waterlily won't grow well with the amount of water movement in there, plus even the minatures will cover an area twice that size when growing well (plus the basket will take up valuable fish room)
try something like Irises, Blue Hygro, or Japanese rush. with a few marginals going over the sides.
good pond for a swarm of golden mountain minnows though, would look awesome and they would love to play in the current.
plus Moors are not the best choice for outdoor ponds as they get picked off by predators easily (no upwards vision)
and Shubunkins are not slow growing as they are just a multi coloured version of a comet, i.e. very fast and genetically very strong.