I am trying to make my goldfish a bigger home without spending a whole of money. I took a rubbermaid like storage container and used an existing penguin 330 filter may add a wispher intank 10-30i if the penguin is not enough.

ofcourse when I filled it up it bows out someone said to get the rachet type tie downs. I dont know if I did it right or not it still bows out.

I was thinking bout a wood frame but wouldnt know if i needed it where I can just put it over it or put the storage container in it. make the frame with with a bottom and set the storage container in it.
If I go that route would I just measure the container and ask for that size wood? and what type of wood would be best. would the container last a long time like that or would it be best to change out the container so often like every yr or so if?

here is the pond thing so far

It depends on a couple of things. First do you want it the look aesethicial nice and how long you are going to keep the fish in the rubbermaid?

If you ain't worried about looks and cost is a factor then you could opt for some treated pine made for the garden and fences. The fish may get too big for the current tub and you may have to do it all over.

But generally stick with pine and plywood. I would stay away from MDF or chip board as when they get wet it's no good.