There are so many different theories on this one that you will get differing views.
Personally I use pond plant soil(almost clay) mixed with silver(silica) sand, I get very good results from this and it is cheap. 8)
[glow=Blue,strength,width]WOW! Fishman that's some really pretty gravel! I think it's the best I've ever seen. In every planted tank I've seen they use clay or flourite.
Recycled glass? now where have I heard this one before.
Looks good,expensive,too coarse,sharp edges,nothing for the plants to root in, the list is endless.
8)
Kitten the best substrate for corys is sand, I use silica sand that is quite fine available from garden centres, you do not need to buy the expensive stuff with pretty pictures of sweet little fishies on them. > 8)
Whats this about algae not growing on the glass? In my 30G I have algae growing on my glass sides, why shouldnt it grow on the glass gravel. Besides, the glass gravel definitely does not look natural. Looks like the north pole! Its a very cold look! If algae is not suppose to grow on it, will bacteria grow on it? Gravel is one of the main sources of bacteria cultures to grow on. I dont like the light reflecting off it either. I would get too bright in a planted tank.