I have a 20-gallon tank with a group of mollies, and just a few days ago, one of my female mollies gave birth to fry. I wasn’t fully prepared for this, and now I have about 20 tiny fry swimming around in the tank.
I’m a bit concerned because I’ve read that adult mollies might eat their young, and I want to make sure I do everything right to care for them. Right now, they’re still in the main tank, but I’ve added some extra plants and hiding spots for the fry.
Here are a few things I’m wondering:
Should I separate the fry from the adults? If so, what’s the best way to do that?
How should I feed them? I’ve heard about using powdered food, but I’m not sure how much or how often.
What water parameters should I be most mindful of as they grow?
Any tips or advice from experienced breeders would be greatly appreciated! I really want to give these little guys the best chance to grow up healthy.
Thanks in advance! 🙂
Yes, you should definitely consider separating them from the adults. While mollies can be good parents, they’re also notorious for snacking on their own babies if they’re hungry or stressed.
Here are a few options for separating them:
Breeder Box: This is an easy solution if you don’t have a second tank. The fry stay in the same water, but the adults can’t get to them.
Separate Tank: Ideally, a small 5-gallon tank with a sponge filter (you don’t want a strong filter sucking them up).
More Plants: Since you’ve already added hiding spots, this will help a lot. Floating plants, moss, and dense structures can give them a fighting chance.
For food, you can crush up flakes or buy specific fry food like Hikari First Bites. Feed small amounts multiple times a day, like 3-4 times. You don’t want uneaten food to rot in the tank.
For water, stable parameters are key! Keep the ammonia and nitrites at 0, and nitrates below 20 ppm. You’ll probably want to do frequent small water changes, but be gentle so you don’t accidentally suck up the fry. Good luck!
I’ve bred them for years and david is spot-on. Separating them is really the best way to ensure they all survive. I personally use a breeder net that hangs inside the tank. It’s easy and keeps the fry safe without stressing them out with different water.
Feeding-wise, YES to Hikari First Bites! Just pinch a tiny bit and swirl it in the water near the fry. Also, you can boil an egg, take the yolk, and mash it into a fine powder. Fry love it, but just don’t overdo it. You don’t want the water getting cloudy.
And for water, mollies love slightly harder water with a bit of salt, but if you’re keeping it stable and doing regular water changes, they should be fine. Keep it clean and don’t overfeed, and they’ll grow fast!
Honestly, if you’ve got plenty of plants and hiding spots, you might not need to separate them at all. I’ve had plenty of fry grow up in a community tank just because they had places to hide. Of course, that does mean you’ll probably lose some of them, but it’s the natural way! If you’re okay with that, then I’d say just keep an eye on things and maybe add more plants like hornwort or java moss.
For food, crushing up the adult flakes until they’re powdery is fine. Feed them small amounts several times a day, but make sure it all gets eaten. Uneaten food is a killer when it comes to fry tanks.
Oh, and make sure your filter isn’t too strong. Baby fish are terrible swimmers, and if the filter’s sucking too hard, they’ll have trouble. A sponge filter is best, but if you can’t get one, cover your filter intake with a sponge or pantyhose to keep them safe.
Thank you
The concern about adults eating fry is legit, but I agree with others that if you’ve already got a lot of hiding places, you might not need to remove them right away. Some will get eaten, but nature’s a little harsh like that. If you want to save them all though, a breeder box or separate tank is better.
As for feeding, I’d also recommend live foods like baby brine shrimp if you can (after a week). They’re super nutritious and help fry grow faster. You can hatch your own brine shrimp at home with a little setup, and it’s totally worth it if you plan to breed more in the future.
I’m with Adarsh on this one. 🤷♀️ If you’re not super attached to saving every fry, just leave them be in the tank. In nature, not all babies survive, and it’s totally fine if a few get eaten. The strong survive, and all that. Plus, mollies breed like crazy, so trust me, you’ll have more fry soon enough. 😆
If you do want to give them the best shot though, a breeder net or box is the way to go. And feeding? Hikari First Bites is great, but I’ve also just used crushed flakes and my fry were fine. Just be careful not to overfeed! Fry are messy eaters, and too much leftover food will mess up your water fast.
I’ll chime in with a slightly different suggestion: if you’re serious about breeding and raising fry long-term, consider investing in a separate grow-out tank. It doesn’t have to be huge, but having a tank dedicated to fry allows you to control the environment better and raise them with less stress. You can use a sponge filter and heater to create a safe, low-flow environment where they can grow without any predators around. Feed them several small meals a day — crushed flakes are fine, but live foods like baby brine shrimp or microworms will make a big difference in their growth rate.