cycling questions.

zebra danios might be ok for cycling if you're gonna use a fish, but they will definitely not be happy. they'll be cramped in a 10 gal.
k, i just got 2 zebra starfires, and a load of water from the tank of the lfs to help the cycle. they seem to be pretty happy they move A LOT or maybe because the current of my tank is strong since i have two filters. i dont know, but they arent eating the flakes i drop them.
 
tank water from an established tank will do practically nothing for you. good bacteria doesn't live free-floating. they're on media, gravel, plants, fish, basically any surface area. not in the water. the amount of bacteria you got in that water could've been gotten from a pinch of gravel frankly.

danios are active swimmers, that's why i said they'd be cramped in a 10. resist the urge to keep feeding them. they'll always inspect food even if they're not hungry.
 
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