wow cant believe this thread got got so popular.

Anyway I found the answer you guys are looking for.

I contacted Makerjuice.I received an email back and they told me that you can use all sorts of fillers

he said the Fillers will make the viscosity of the resin a bit higher
he said some examples you can use glass microfibers, ceramic nanospheres


on my own search I found a type of resin filler called Microbaloons which are almost the same as Ceramic Microspheres.

this is a video of somebody adding resin filler to there resin this type seems to be a very light weight.
To me it seems to be allot of trial and error to figure out which is best to mix in to get the best results.