I find it hard to count the amount i put in with females giving birth all the time but i can tell just by looking. I also remove bigger fry weekly and add fry weekly so it's always balanced. On average i have about 25-30 fry(with 3 pygmy cories) in my 10 g.
i must be the luckiest person here! my guppy only gave me 2 fry... I hve them 2 in a ten g. My other mom is about to pop tho, so we'll see how many she pops out!