Originally Posted by trishalove
I do think she was stressed. She was pregnant for what seemed an eternity - finally I noticed a few fry - only 4 to be exact. They were born at different times - they are all different sizes. I don't think she ever had the rest - there had to be more - or they were expelled as eggs if that is possible. The water params are fine - I test them all the time. I change the water on a regular basis - 40 percent once a week. The guppies I had were multiplying so I finally gave away most all the guppies and two of the molly fry this morning. So currently, there is one molly - 2 molly fry - 3 male guppies - 5 neon tetra, one platy and one cory in a 20g. I plan on no more fish so I hope this will be a happy environment.
She could of given birth and then had them all eaten. This is common. Its also common that she won't get a rest. They can give birth monthly for 6 months+ at a time.
Its good that your trying, however this won't be the happy tank your looking for:
The two molly fry tend to like more salt inside of their water (aquarium salt would work), however cory's don't like salt and are sensitive to it, and tetras don't like it even more.
Cory's are schooling fish and the fact that you only have 1 of them in the tank will not be good for them, and as a result can end up hurting them. For the tetras I would recommend getting at least one more.
Here's what I recommend:
3 male guppies
6 neon tetra
If you can, even though its harder I would recommend making the tank all livebearers, or just like corys and neon tetras. The reason for this is corys and neon tetras tend to favor lower, slightly more acidic pH's while livebearers tend to favor higher more alkine pHs. 7.5~ is good for livebearers while 6.5 is good for corys and tetras, however you can keep them together if your careful.
I would recommend testing your pH to see what you have and then going with one of the two following:
3 Male Guppies
2 Molly Fry (if ones a male and the others a female when they grow up, I would recommend getting 1-2 more females so that the current female isn't hurt by the one male)
some ghost shrimp, or red cherry shrimp.
6 neon tetras
some ghost shrimp or red cherry shrimp
Best of luck, and I hope this helps!