Welcome to the hobby! Yes, plenty of people learn the hard way that livebearers breed like nuts - also be aware that once a female guppy/molly/platy has mated with a male, they can store and use sperm packets for months afterwards, even with no male around, so your adult female could continue to have fry every 6-8 weeks for a long time - even up to a year.
You can tell male and female adult livebearers apart by looking at their anal fin- females are fan shaped, males have a pointy fin/sexual organ (called the gonopodium) there. But bear in mind that babies will all look like females at first, it takes a few months more male mollies to develop the gonopodium.
So you may want to consider rehoming or returning the adult females if you're not set up to handle a lot of fry. As you've seen, the fry don't always get eaten! And it's easy to get overstocked.
From your photo, your main problem seems to be lack of tank maintenance. Not knocking you at all! You're new to this. Do you have a gravel vac, and know how to use it to clean the substrate?
Like this:
When the tank is dirty, as the substrate is in that pic, algae then has plenty of nutrients to thrive. It's not great for the fish either, so it's important to give the substrate a good clean while doing a weekly water change of around 50%. Get a tank cleaning kit and it should include a scraper with a metal edge to remove the hard algae from the glass.Once the tank is cleaner and you're in a routine of doing weekly maintenance, it's worth considering adding some live plants to the tank. Live plants will compete with the algae for nutrients. Some algae is normal though, it's just what happens in a tank of water with light on it - even more if the tank is getting direct sunlight from a window? The trick is to learn how to balance the tank so the algae doesn't get out of control, and you're the best weapon for that.
You can tell male and female adult livebearers apart by looking at their anal fin- females are fan shaped, males have a pointy fin/sexual organ (called the gonopodium) there. But bear in mind that babies will all look like females at first, it takes a few months more male mollies to develop the gonopodium.
So you may want to consider rehoming or returning the adult females if you're not set up to handle a lot of fry. As you've seen, the fry don't always get eaten! And it's easy to get overstocked.
From your photo, your main problem seems to be lack of tank maintenance. Not knocking you at all! You're new to this. Do you have a gravel vac, and know how to use it to clean the substrate?
Like this:
When the tank is dirty, as the substrate is in that pic, algae then has plenty of nutrients to thrive. It's not great for the fish either, so it's important to give the substrate a good clean while doing a weekly water change of around 50%. Get a tank cleaning kit and it should include a scraper with a metal edge to remove the hard algae from the glass.Once the tank is cleaner and you're in a routine of doing weekly maintenance, it's worth considering adding some live plants to the tank. Live plants will compete with the algae for nutrients. Some algae is normal though, it's just what happens in a tank of water with light on it - even more if the tank is getting direct sunlight from a window? The trick is to learn how to balance the tank so the algae doesn't get out of control, and you're the best weapon for that.