Hi Tim, Layton
The plastics place is Award plastics on (wordsworth street i think). The glue that we used to use at work was Quickbond and it comes in several different grades and has a cross referance to Weldon. From memory it was quite cheep about $17 for 250mls. We used to ues it for glueing Acrylic pipe to pvc for lage sight glasses 250mm NB pipe at 20meters head so it will hold up for most things in a tank.
Dave.