Take it if it's free or cheap.
Then, measure and get class cut to serve as dividers. Any glass shop can do this. Get something break resistant and have them smooth the edges. Or, cut plexiglass yourself. Remember, though, plexiglass scratches easily and discolors.
Buy a tube of aquarium caulk. Make SURE to get aquarium caulking. It has fewer fumes or something - don't ask me the details. It's been years since I did this type of thing and it's not on the edge of my memory.
Have a helper hold your glass or plexiglass dividers in place while you silicone them in. This basically serves to glue them in place. Just MAKE SURE you have them where you want them. Once the stuff dries it's horrific to get the divider out - you'll be cutting for hours with a thin edged blade and still may not get it out.
Hold in place until it's not going to fall, or have something rigged to hold it in place.
Voila! Divided tank. If it's six foot long, I'd divide into thirds & put a pair of buttons in each 1/3. I would not try to put enough for a dozen in, though. You might be able to do 4 compartments. Depends on the tanks measurement from front to back.
How wide is the tank from front to back? If it's 20+ inches you might be able to squeeze an additional divider into it.
One problem I do forsee is cleaning this sucker. It's going to be a (language probably not acceptable here.) If it's a TALL tank then it won't be easy. If it's a short tank, it won't be bad. Aquariums of this length can be a foot tall or 3 foot tall...if it's on the taller end, forget the whole dang project.
You'll want to make your own top for this, too. You'll need to be able to open the individual compartments SEPARATELY. DO NOT expect to take the top off this thing otherwise. Buttons will pop out of the various compartments while you're trying to work in another. Then you're going to hate button quail really quickly.