Setting up my 190gal (still a newbie)

[TheReefGeek]

Keep the 55, especially if it is the 4 footer. Assuming you want to keep everything under your stand, having a seperate fuge and sump can be difficult. Great if you can do it though.

You could partition the 55g with glass or acrylic dividers to make skimmer, fuge and return sections. Make the fuge as big as you can, which means you have to decide your "ultimate" skimmer so you know its footprint so you can size the sump accordingly.

Yes you can use rubbermaids, but strong ones that are food grade would cost more than you will get for the 55g. Plus setting up dividers in rubbermaids that are not square is difficult, especially because the sides bow out when you add water, then you have to brace them with wood, etc..... not worth it IMO.