Hello and welcome! Yay for another Floridian too!
I had three long finned zebra danios for awhile and they seemed fine in a standard 20g, I have 5 now and they seem quite happy with it, so there should be no worries there.
I would invest in the test kit that comes with the droppers, it ran me around $30ish for pH, ammonia, nitrite, and nitrate testing, that will be a huge help to checking the levels of nitrates which is a primary (as far as I'm away) way to tell when a tank is fully stocked, as well as dictating how often you will need to be doing water changes. It'll also be a huge help in determining when the tank is cycled and when it will be safe to put fish in. I would stay away from the test strips, my first set was horribly inaccurate.
I would think that even with the additional tetras it may very well be fine. Just remember to add the fish slowly, maybe 2 or 3 at a time once a week at shortest and watch them. I will say that I have around that level of fish in my tank, but I also have a planted tank so the nitrates are being used almost as quickly as they are being produced.
Originally Posted by JamesFl
It is kind of overwhelming reading all this information but I am the type of person that wants to know as much as I can before I actually persue something.
This is always good to hear, an ounce of prevention is worth a pound of cure, this will prevent a lot of frustration. :)
Welcome once again to the forum!