iv got a 60litre tank atm with 9 small goldfish and 2 plecos and was wanting to buy a bigger tank what size should i get

well duh!!

THE BIGGEST ONE YOU CAN AFFORD!!!!

bahahahah i was looking at spending around $300 for 115 litre tank down the road with stand and hood is 115 litre big enough

rule of thumb i run with is 1.5 square ft of tank bottom per male BN, and 2 females per male. volume isn't realy so much of an issue, its bottom space.

I dont know much about goldfish but i believe the get big so it may not be big enough for them, but it will be for the BNs

What are the SURFACE dimensions (length x width) of the tank?

As a guide, for Goldfish in a coldwater set up, you should allow:

60 square cm for each 1 cm of fish body length excluding the tail
or 24 square inches for each 1 inch of fish body length excluding the tail.

This will increase if you are heating the tank.

9 small Golfish, could potentially become 9 large Goldfish needing a very large tank, or pond.