No. We should not compare the bulk density of martial with the density of water. In general, if the density of material has more than 600 g/L, it has to sink.
Pellets have a density of 600g/L when considering their dry weight. I guess while floating in water the pellets usually absorb water and their density increases from under 1000g/L to over 1000g/L and they sink. Maybe your pellets do not absorb water in the same manner and their density stays under 1000g/L. I think it is important to take into account how fat contributes to the 800 g/L, as fat has a lower density than water and does not dissolve in water. Anyway, any material with a density of 600 or 800 g/L will always float, and yes, you always can compare the bulk density of material with the density of water, its g per L.