Check the history of the fishes at the lfs. If they are tank raised (most are) esp if they are tank raised locally they will be well adjusted to your water. If they are from florida or similar and were raised in soft water they might need more time to adjust.
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As other said definitely the 10; the kribs and apistogramma will not get along. I have kribs and apistogramma in a 40B and it is a mess and neither are breeding age yet. I'm going to move one of them to another tank soon. At least my kribs are not friendly fishes and i'm sure they will be a lot worse when they become sexually mature.
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My favorite tank for them is a 20 long. If petco is having a dollar sale (I think they might) then you might consider getting one for $20. The 10 works of course but a 20 is really good for live plants and you could make quite a nice tank for them. Also - at least our local petco - has some really nice
drift wood with areas under that can be used as
caves - for a few dollars. It is somewhat soft wood so it won't last forever but the apistogramma will love the addition (look for a piece that is partially hollowed out underneath).
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Anyway some suggestions but i guess a lot depends on your budget.
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