pregnant black tetra

Question
Hi There,

I have had a 30 gallon fish tank for 10+ years. I recently noticed that one of my black neon tetras has a huge belly. Everything seems normal, eating well with lots of activity but i do think that she's pregnant because of her size. I went and bought an isolation tank that allows the eggs to fall to the bottom of it so she doesn't eat them but, after she lays the eggs, how do they get fertilized or do they have live birth?
If i do need to get them fertilized i am wondering if any male will do the job. I have about 5 of that particular breed and am not sure who's male and who's female.
Let me know what you think, I guess that i will leave her isolated until i see some changes but i just don't know what to do if she does lay eggs.
I keep my tank at a regular temperature of 74 degrees, with active air and water filtration systems. There are several other breeds in the tank - penguin, red & black finned tetras and some platys. I only change the water when i clean the tank - maybe every couple of months. The water is clear and i haven't had any disease issues for several years now.  
Thanks so much for your help and i will keep my fingers crossed for babies lol!

Answer
Katherine,
Tetra's are egg layers. This means, the female lays the eggs and the male fertilizes them. If she lays the eggs and no male is there to fertilize them, they will be eaten. The best thing to do is let nature take it course. If she lays the eggs in the tank, and there are no hiding places for the babies to go to once hatched, other fish will eat them. Water changes should be done weekly by removing 25% of the water replacing it with clean conditioned water. If you are cleaning only every few months, the water conditions will not be good for the fry(baby fish).