New 125 Gallon...filter/sump recommendations

[my5girls]

I am setting up a 125 gallon tank, will be fish only with live rock. (for now). Ive been out of saltwater for 15 years now. I bought the Fluval FX6, but haven't set it up yet, as I'm currently painting the back of the tank....I used to have a wet/dry filter. I plan to use a protein skimmer also. Would like to add that to the sump with the heater and such. I cannot build a sump, I need to buy one. I only only have 2 cubes that will hold a sump 21 wide x 23 tall x 17 deep, anything that fits these dimensions I can buy. I could accommodate 2 of them at those dimensions. Also any recommendations on Protein Skimmers?

[DreadCapn]

WB to the hobby. I'm in the process of setting up my first tank, but from everything I've read, these days most people will say to go ahead and return the canister filter, as it does more harm being a nitrate factory than anything.

Can you explain more about your sump space? Realistically you're probably able to get 15 gallons in a single 'cube', and even x2 isn't really large enough for a 125 gallon. Pictures may help, because this is really "How can I fit a bigger sump into my space" I think.

As for Skimmers (and sumps themselves), it may depend a lot on budget. I am getting a Reef Octopus myself.

[mcgyvr]

Bubble Magus Curve 5 skimmer (or the Curve 7 if you plan on a bunch of fish in that tank/heavy bioload)