Fry Rubbing On Gravel

I noticed after I did a water change that my almost month old fry are rubbing on the gravel. There's no other signs of anything. None of my main tank fish have anything. So I'm confused. I did a really good vacuum earlier because my nitrite was high. Tested it again afterwards and everything was at 0 Ppm. I'm just confused .... I don't see how they could have caught anything. Are they just feeling good or something?

I've noticed that flashing/flicking could mean a few things:
Parasites, or a disease
High ammonia
Or, mostly in livebearers, I've noticed, then seem to flick right in and after a WC. I don't know why, but my male molly charges around the tank during a WC, flicking occasionally, then settles down. I have no clue why xD
 
I'd just keep an eye on him.

Well my ammonia is at 0 Ppm. So it can't be that. And I can't see how they would get a disease wheb everyone is super healthy. Maybe it's just they're all hyped up. They actually seem to have stopped for a little while. And they're live bearers swordtail. So maybe that's just it! I think they just feel good because the waters so clean. Including the rocks lol
BTW my new red swordtail fry! 3 days old
I have around 30!
Pictures are from birth to now.

 
Or, mostly in livebearers, I've noticed, then seem to flick right in and after a WC

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Now that you mention it my Mollies in the big tank sometimes do that.
 

 
I have around 30!

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Oh my that's a lot of fry. I’m a poet and I didn't even know it. I can't make rhymes all of the times.
 
What are you going to do with all the fish Ariel?

So many babies!! What's the gh of your water?? I really want to try livebearers sometime, but my water is fairly soft...I wonder if they would adapt.

I don't know the exact GH it's a somewhat harder. They're really easy to breed you should try it! It's really rewarding. As far as what I'm doing with them ... My lfs will but them off me! I'm really enjoying breeding fish and I might just try another kind here soon. Maybe my angelfish
I think they would be okay with your water. Although I'm not 100% sure.
I think there might me more in the tank. I could only catch like 30. My month old fry were eating them so I thought for sure I'd come home to none. But I looked and saw some! Then I saw More... and more!

platies are better at coping with softer water than say guppies or mollies. I kept platies for a long time in my really really soft water and they did alright. I had them 2 years plus and had far too many fry from them.
 
The fry are looking good Ariel, I've no idea why they are flicking but the Nitrite reading you mentioned might have something to do with it. Keep an eye on the Nitrite now that your aware of it and hopefully the flicking will come to nothing

Everything was level before I put the pregnant female in there. So I think that's why it had a spike in nitrite. I tested it again this morning and everything is still at 0 ppm. They have stopped doing it as well. I'll just keep an eye out for anything suspicious lol. I wouldn't want anything to happen to my new fry.

the adult female will have a much bigger bio-load than the fry and so, yes, I'd expect there to be a potential for things like this. It might be an idea to run a small spare filter in your main tank that you can move over with the pregnant females when you need to. That would help to support the fry tank filter whilst the adults are there putting it under stress.
The fry tank filter will increase it's bacteria as the bio-load increases as the fry grow but it will only do that very slowly. Hope that makes sense ... I'm tired and my brain is on a go slow!!

I will Def try that! I might put some more medium in from thr main tank into the fry tank as well.
Just put other female in the tank. She's due here soon. And I'm going to let them be this time. And whoever survives, survives.

the filter will only have enough bacteria to support the day to day stock so if on a day to day basis there is just a few fry with a tiny bio-load there will only be a small amount of bacteria within the filter.
An adult fish will have a bio-load far far higher than tiny new fry and so each time you move your female in to the fry tank to give birth the ammonia produced goes up massively - the filter isn't able to cope and so you see readings of ammonia and nitrite. 
 
The best way to deal with it is to have a small additional filter within the main tank which is developing bacteria for adult fish. Once the small filter is cycled to adult fish you can lift it out of the main tank and add it to the fry tank (in addition to the existing filter) when you move in the female(s) to give birth. Once the females are moved out you can move out the small filter with them. 
 
Doing it this way should stop the spikes. Hopefully I've explained that a little bit better

No it makes total sense! I will Def try that.

I have one little fry that seems to not want to swim ): don't know if he'll make it. Don't mind thr mess it was feeding time. Gets cleaned afterwards. But all the rest of the fry go to the top and feed except him. Hopefully he is just a late bloomer! He doesn't have a plump belly like the rest. So I don't think he's eating. ):

this is the downside to breeding ... you will get fry born deformed and the dilema of what to do for them is awful. For now I'd leave it to Mother Nature - she always knows best

I know ): if he doesn't start swimming soon I might release him into my main tank. As horrible as that sounds it's what happens in nature. He could just be a late bloomer. So we'll see I'll give him some time