Black Molly Babies all died, wondering why

About 3 weeks ago my molly had babies, about 50 of them. They have been happily living in the floating breeder tank alone since then. This morning my husband found our Beta in the breeder tank so he scooped him out. Now to protect the babies, or so I thought, I placed the lid on the floating breeder, yes it does have holes in the top. A few hours later all my babies are dead. Any idea why? Everything else in the tank is fine and water levels have not changed. I am baffled (and upset at the loss of my little ones)

 

I see you don't know about the nitrogen cycle. Definitely read up on this... it is very important to fishkeeping. How long have each of your tanks been set up?

 

I am familiar with he cycle, when I said levels have not changed I was referring to chemicals, they are tested everyday and nothing changed. The tank has been set up over 10 years and have never had any problems. The only thing I can assume is that when I placed the lid on the breeder. although it had holes, it was not enough "air" for the babies since there were so many in the breeder. "Mom" is pregnant again so we will not be placing the lid on the breeder this time lol

 

could you add a air stone to the fry holding area ?

 

What are your readings for ammonia, nitrite, nitrate and pH?

 

you could drill small hols in the breeder for circulation or put them in a net that way the water in the breeder is clean filtered and oxygenated or at least as much so as your tank

 

I agree with the above... put an airstone in the breeder box thing.

 

Sorry to hear about your loss. I have black molly fry in my 29 gallon and some sunset platy fry in my tank with one black molly and one sunset molly and I don't think I have lost many. I have never seen the adults chasing the fry. they are just about big enough now that they would be hard to eat.