Why are my guppies swimming so rapidly

[Owp]

I have a 25l tank and only just got the fish yesterday - 4 male guppies and 4 neon tetras heated and filtered. I am just wondering why my male guppies are all darting around the tank up and downwards. I have experience with other fish because I also have a 60l tank also. Please help...

 

[Owp]

Also another thing is my neon tetras aren’t coming up to eat I feed the fish tropical flakes and they just stay where they are? Do I need to get dinking pellets?

 

[Mpwallace1]

My 6 neon tetras never come up to the top in my planted community tank. They hang down on the bottom or about 6 inches up. There’s no bullying what so ever in the entire tank so they are not scared. Get sinking micro pellets and they will love them down there. I grind up some of the flakes on occasion into small pieces and they find those down there as well

 

[Owp]

Do you have any idea why the guppies are swimming so fast up and down?