Do platys sometimes hang out at the top? Water parameters seem fine.

I have 4 platys, & today I noticed they're all hanging out at the surface. My other fish bud's are doing their thing business as usual ( 6 tetras, 5 corys 1 snail). But every platy is at the top. All of the fish have lived harmoniously for a while, so I don't believe they're avoiding their tank mates. I tried to snap a picture, but I spooked two of them, & two stayed at the top. I'll attach the water test I just did, plus the two fish that I was able to photograph. Any thoughts are appreciated!

Some do

Serial hobbyist said:

I have 4 platys, & today I noticed they're all hanging out at the surface. My other fish bud's are doing their thing business as usual ( 6 tetras, 5 corys 1 snail). But every platy is at the top. All of the fish have lived harmoniously for a while, so I don't believe they're avoiding their tank mates. I tried to snap a picture, but I spooked two of them, & two stayed at the top. I'll attach the water test I just did, plus the two fish that I was able to photograph. Any thoughts are appreciated!

Click to expand...

Hello Serial. Livebearing fish are top feeders. They're most comfortable when they live in a tank that's heavily planted on the surface. Their fry are typically born in the upper middle area of the tank and then they swim to the top to get their first breath of air and to hide in the surface plants. Your tank has no plants on the surface, so any fry you might have will be easy prey for the larger fish.

10 Tanks (Now 11)

Sometimes they do, but anytime fish other than like, gourami or kilifish are hanging at the top, especially if it's unusual, is to check the temp of the water/heater is functioning normally, and that there's enough surface disturbance to allow for oxygen exchange. Warmer water temp means the water holds less oxygen, and I caught a malfunctioning heater before it boiled my fish when I noticed a lot hanging near the surface gasping and found the temp had gone from 76/77F well into the mid 80s and climbing. So always worth checking the water temp first.
It looks as though your filter provides a good amount of surface disturbance, so oxygen not likely to be a problem. Do the fish seem to be gasping at the surface? Or just hanging around hoping for food?

I agree with @10 Tanks that some more plants filling in the height of the tank and/or floating plants will give any fry a place to hide, but also make the other fish feel safer and more secure from the overhead predators that they don't know aren't there!

Thanks for the responses! I checked the temp as well, it's holding steady at 78. This is unusual for them in the sense that they usually hang out toward the bottom, constantly picking at various food they can find.
I have a hang on the back filter which seems to supply a lot of oxygen, but maybe I'm wrong?
I do want to put some floating plants. Any suggestions? I think the one platy has been pregnant prior to me getting her. she's super duper round, & I think I can see a gravid spot (maybe). I did recently cut back on feeding, because they were constantly munching on the sinking cory food.