I had some trouble with blue gravel having tiny specks floating at the top of my tank, luckily I found this out while filling it for the first time.
throw the gravel in a strainer, like 1/4th of it at a time. Throw it under the water and sift it like you ar elooking for ggold. All the specks shoudl wah away
If you want to cycle the tank use gravel, the glass beads just cause algae unless you do 100% changes every so often and clean them :-/ I always take the lazy route and use gravel with the beads on top haha.