There are 3 MFs that you can have in level one. For the sake of not "spoiling" I won't say which. One of those breeds will not live long, so sell!!
Level 2 will take the pressure off and let those fish live longer, but you really can't get the other 4 MFs until you hit level 3. SOMETIMES you can get one of them in Level 2 but they generally don't live long enough to even be officially 'discovered'.
Hope that helps.

Marcey