Why she stick to the upper part?

[poothebear]

Does it look like she is being sucked into the intake? Or does it look like she is just playing?

Neither. She didn't eat so probably not just playing, and seems like she chooses to be there

 

[poothebear]

Weak fish get pulled toward filter suction, there's something wrong with the fish, you can tell by the very pale color.
How long has the tank been set up, how was it cycled, and how long have you had the barbs?

It's a typical color for a female rosy barb. It's older than a month and the amonia/nitrit are really low so Cycles is probably not the reason

 

[Essjay]

the amonia/nitrit are really low

What are the actual readings? Ammonia and nitrite should be zero. Any reading above zero, even if it is low, is harmful to fish.

Have ammonia and/or nitrite been more than zero in the tank water at any time since you got the fish?

 

[Slaphppy7]

It's a typical color for a female rosy barb. It's older than a month and the amonia/nitrit are really low so Cycles is probably not the reason

She's suffering from ammonia/nitrite poisoning, if that's the case

 

[poothebear]

Here is an API test stick result, seems to me like Nitrit & Nitrat are below 15

 

[Essjay]

Nitrite looks to be zero, but test strips don't include ammonia. Do you have a tester for that?

Has there ever been a reading above zero for ammonia or nitrite at any time you got the fish?

 

[poothebear]

Nitrite looks to be zero, but test strips don't include ammonia. Do you have a tester for that?

Has there ever been a reading above zero for ammonia or nitrite at any time you got the fish?

Never tested ammonia and got my sticks 2 weeks after getting the tank. Sorry, can't tell

 

[Essjay]

It is very important to know the ammonia level in the tank as any level above zero is bad.

How did you get the tank ready for fish, did you add ammonia to grow the good bacteria or did you just set it up then get fish?
The reason we have been asking all these questions is because unless you prepared the tank before getting fish, they would have been exposed to ammonia and nitrite which will weaken fish and sometimes kill them. If you did not cycle the tank, what you may be seeing is a fish weakened by ammonia and/or nitrite.

 

[poothebear]

Due to some specific circumstances I had to move them right away when the new tank arrived, the old filter was also placed in the new tank + 20% weekly water refreshment

 

[Slaphppy7]

You need to get a liquid test kit

API® | FRESHWATER MASTER TEST KIT

The API FRESHWATER MASTER TEST KIT measures the 4 most important levels in freshwater aquariums quickly and accurately, including pH, high range pH, ammonia, nitrite, and nitrate.

apifishcare.com