Yes More Sump Questions :-)

[Nalaundi]

K so my best friend is giving me her 30g tank which I want to set up with a sump. I will be using a wroght Iron stand built for 2 aquariums. my sump will be my old 20g tank.. underneath. now I now I will need a return pump at 5x at given head... havent figured that part out yet but that shouldnt be a problem. I am going to drill my 30g for the sump. do I need to drill the 20 gallon or can I safely get away without.... thoughts... and what pieces exactly will I need for the pluming aspect of this. what size of holes in the aquarium what size of bulkheads.... what pieces for the pvc tubing parts. obviously elbows strait pieces connectors... it I do ridged plumbing... what about soft tubing... the vinal drain hoses that I see..... just confused on all the little stuff now...lol love some help thanks.