New cistern and own a few question?

Hey, i have recently set up my first tank, it is 3 ft x 18 x 15, it have been up a running for a week now and i have newly added 5 neon tetras and 2 cherry barbs these seem to be male and feminine as the bright red one keeps chasing the other one around which has a enlarged belly is she pregnant? I be only able to get this masses as it was all the local fish shop had will this be an modest number to start the cycling process? The next question i have is that during the week short fish in them i tested it every day and the ammonia would go up to .25ppm and later back down with no change to nitrite and nitrate level, why is this?

thank you
Question something like betta?
Answers:    Sounds like things are working OK

You have a decent size cistern and have only added a few fish. The ammonia buildup should be so slow that the cycle will start before the ammonia even gets dangerous. That is the way to do a cycle beside fish, slowly.

Leave them be for another week, if the readings are still good, win a few more fish. I suggest a few more cherry barbs, they will be happier in a group similar to the Neons.

After that, whatever other small community fish you want, but add them in stages over the subsequent 6 weeks to build up the cycle to match the number of fish.

Ian
Bloated sinking fish?
Hi there
The bright red one is chasing the which id speak is pregnant simply because it is a girl

But sorry i cant help you with the nitrite levels and stuff because i dont know that much!! Sorry!
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