Will all of the baby platies and..

Brief：
I have 2 small (1 inch) platies and 2 small (1 inch) guppies in a small 2.5 minibow. I know its alot for that size, but I change water just a little m.. 

I have 2 small (1 inch) platies and 2 small (1 inch) guppies in a small 2.5 minibow. I know it's alot for that size, but I change water just a little more often. In that tank, for those fish, how much salt should I put. Also, my female guppy might give birth soon, because it has dark black spots near stomach, so if she gives birth in my 2.5 with the other fish, is it sure that every single fry will be killed/eaten?? What are the chances of some surviving? Could I fit like a breeding net or box or w/e in that small of a tank?

A 2.5 gallon container is to small. If you put plants and rocks for the fry to hide in you will have even less water to hold oxygen. Even if a fry is not eaten it will probable be stunted. you can buy a 1/2 gallon hatchery which has a "V" insert which allows the babies to fall thru to the bottom where the motherr can eat them. You can remove the insert and return the mothe back to the main container and put the fry into another tank. Guppies can take moths before they have their fry if they are stressed (and yours are). They will eat their young so that they can regain some of their energy lost in producing them if it looks like they are likely to be someone else's dinner (common in a lot of animals). This is definitely going to be the case in your tank. If it helps, female guppies 'box up' around their anus just prior to giving birth. It may sound strange, but when you see it happen there will be no doubt in you mind.

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