I'm also looking to make a sump for a 55gal tank. I have a pump, media, and hoses left over from a failed canister filter.
I'm also trying to fit the filter in the stand under the 55, The problem is that there is that the space is plenty long at tall but only about 11 inches wide. Has anyone found anything that will work that can fit in that space? I've looked around online and a few stores haven't found anything bigger than a 15 gal tank.