Thanks guys. It's a 20H gal
tank with 9 cardinals, but I did start off with 12. 3 died the first week, not sure if it was my fault, having them shipped, or what, but the rest are going strong for over a year now.
To be honest I really don't test.
I feed them once a day and it's just enough for them all to eat and no more.
I do a 25 percent water change once a month.
Test the water once a month and it's always perfect, and either way I do the water change.
I will post the numbers next time I test.
Maybe it's because I only have 9 small fish in a 20H tank(which I think is a + for both the fish and tank keeper), but these seem very hearty fish.
Fish are so easy to keep as long as you don't overfeed and/or overstock.