You can get it from a fisherman at the fight area.
The Pokemon Platinum guide book says you get it at Pastoria City with a super rod hope i helped
Above Fight Area you'll see a fisherman talk to him
no you can't find a torchic egg in Pokemon platinum
You cannot find zekrom in pokemon platinum
Find a fisherman in the Fight Area It is at northwest area (top left)
keep going to the left 7, up 1 down 2 and up 3
Use a super rod.
The Pokemon Platinum guide book says you get it at Pastoria City with a super rod hope i helped
you can find it on route 220 using the super rod
Pastoria City and Pokemon League, use super rod
Fish at Canalave City with Super Rod.
route 223 - 230 super rod
in the safari zone, use the super rod
You have to use the Super Rod on Route 226.
You can find it by using a Super Rod on Iron Island.
in celestic town use a super rod in the ponds
Use the super rod on the floaroma town side of route 205. I hope this helps.