If you want high quality food, New Life Spectrum or Northfin are the best on the market. I haven't gotten my hands on Northfin yet (already have a stockpile of other food), but from what I hear and see, it pretty much is a replica of NLS ingredients along with the addition of Calcium Montmorillonite clay that Dainichi food's use. Northfin sounds great along with them clearly stating they don't use harmful preservatives such as Ethoxyquin, that NLS won't admit to using or not using.
Here's a good analysis of foods
Northfin Fish Foods Ingredients Analysis
Northfin is a Canada company, but opened up a USA branch not long ago
northfinusa
Similar prices to NLS, but that's the price of quality ingredients.
Only downside I hear about Northfin, is that they aren't tried and true yet, might not know just how good of quality their high quality ingredients are, and I have heard some mention that their fish didn't like it too much because it was hard from the Montmorillonite clay. Only have heard these things, I don't know if they are true.
I still like NLS Finicky Fish formula for the New Zealand Green Lipped/Shelled Mussels they use (sinking 1mm pellet though). Not sure if NLS Thera A has more garlic than Northfin.
I haven't used Northfin or taken a good look at their foods, so I don't know which ones float. But most .5mm pellets will float if placed lightly on the water surface (too light to break through water surface - not sure if the Montmorillonite clay in Northfin makes it heavier or soaks up water faster and sinks quicker, but Philip says they float alright)
I can float .5mm NLS pellets (I use Thera A community fish formula, there is .5mm Ultra Red now too). NLS has 1mm Betta semi-floating pellets and Premium flakes that will float. Most of the other NLS that are labeled Floating, are pretty large, meant for large monster fish.
If you just want any floating food, even low quality, pretty much any .5mm or smaller pellets should float, flakes will float, and I'm sure there are other pellets that say they float (1mm+, but I don't know about/of many low quality foods, besides their ingredients).