Go to the safari zone in west Johto. Use the area customizer and set one of the zones to "Marshland". Then, place 21 forest themed objects in the area. Then, wait 20 days. You can then find croagunk in the tall grass.
pokewalker route
Croagunk is not available in the Pokemon SoulSilver/HeartGold games. Actually, it is. You must put forest objects in the marshland area of the safari zone. I don't know how many though.
Croagunk, Noctowl, Hoothoot, Psyduck, Quagsire, Starly, Staravia, Azurill, Marill, Skorupi and each day, there will be one specific really rare pokemon.
You can't catch bastiodon in Pokemon soulsilver.
Croagunk is'nt in fire red. try diamond pearl platinum heartgold or soulsilver.
catch it? no.
Yes, you follow the Croagunk into the Great Marsh and then catch them.
You cannot catch Heatran in Pokémon SoulSilver, you will have to trade for it.
No, you can not catch Phanpy in SoulSilver. It is a version exclusive to HeartGold.
You cannot catch Celebi in Pokemon Soulsilver, you have to transfer it from Diamond and Pearl (if you have it in those games).
No.
No.