I believe Lalo is actually of similar density as Fiji, they are from adjacent areas in the South Pacific. Generally, you want rock that is less dense over more, because this means it is more porous, and therefore more desirable (it can support more bacteria within it, the principle reason you are getting it). This is why Fiji tends to be on the pricier end compared to Florida or Tonga/Caribbean. I am not as familiar with Lalo rock, but I think it is actually a city in Guam. I don't know why it is so special, it appears from the DrsF&S site that they are promoting it for the interesting shape.