koura won't climb out of a smooth sided bath
but can climb on plants and if bath is full to the brim climb out then
watch for over flowing in heavy rain
you could drill bath below the rim and attach an over flow with strainer to stop inhabitants escaping
cast iron rewires slow drilling with heaps of grunt
number of fish will be dependant on how clean you keep the water
water changes and moderate feeding
had my eels and kokopu etc in this