Tankmate Suggestions ?

I have a newly cycled 90l tank 24" x 15" x 15"  with hard water, (LFS says all fish are acclimatised?) containing two handsome Platys and hope to get four or six more, some hi fin ones, so some months down the line, i would like a contrasting group of fish, say 6 or 8, i would really like black and white, like penguin, emperor or black neon tetras, or Zebra danios, something a bit more lively than platys, even considered guppies, and corys (have smooth but not fine gravel) can anyone sugest suitable candidates that are not likely to fin nip the hi fin platies or be too aggressive. Tough one i think 

Thanks FC is gravel an issue with the corys though ?

Thanks Sue, yes thinking further down the line here, two more platy next (guppy and endler gone back to shop)

Happy whiffling sounds good to me 

Panda cities do get a lot of love on here, have a look at Julii Cories, which are for me the best looking Cories and have bags and bags of character. I'm having 10 of them when I'm allowed.

Oooh i think with ten of them it will be Panda Cory city  and thanks Resa, i'm begining to think cories will have to be for another future bigger tank maybe, perhaps as well if i learn the ropes with Platy and Tetras and then down the line if im still hooked and more experienced i will have lots to choose from.