Sand ,gravel Or Slate?

[GhettoFish]

So will be re arranging the tank soon and just dont know what to go for ,will be getting some guppies and neon tetras hopefully.I have an undergravel filter and also a fluval u3

not sure if sand will be suitable will the undergravel filter?

always like the look of black gravel as do the slate

not sure where to get the slate if i went down that route

 

[Destination Doha]

hi GhettoFish sand is a no no whith ugf the other 2 whould be ok imo black gravel looks best realy brings out the blues and reds of neon tetras