I would not run Floss in a Fluval unless it's a very low-waste tank. The tiny surface area of the baskets means that floss will clog fast if any reasonable amount of waste finds it's way into the filter. Fluvals aren't the easiest filters to work on IME, so I like to avoid touching them where ever possible, so don't like running media that makes them "high-maintenance".
Sponge can be bought under any generic brand and cut to fit. A medium-to-fine sponge will give slightly better mechanical filtration for minimal maintenance increases and may be a worth while addition
Ammonia Remover is Zeolite, and a dangerous media to use in many situations. Unless the filter is to be used in a QT tank that required sterile conditions and no medications for some reason, I'd give that media a pass
I personally wouldn't permanently run Charcoal, or Activated Carbon, as it requires very regular replacement to remain effective. It's done most it's reasonable work in the first 12 hours... After that it is effectively scrap unless you are going to add a lot more of what it's in to remove in the near future... I keep it on hand for if I ever need to remove medications or suspect poisoning for what ever reason though, it's good for that type of application
Biomax is a good all round biological media. For a low-maintenance set-up, I'd use the four supplied sponges in the foam pre-frame and them all biomax in the other trays
