Sick female guppy

[agrownupsupposedly]

My female guppy took sick over a period of couple of days - she is now very skinny and hardly eating anything and stays right next to the surface. There is some kind of redness near the back of her head. Other fishes are okay. Any ideas on what could be going on?

(0 ammonia, 0 nitrites but but have some nitrates but keeping it under check by weekly partial water changes)

The 6g tank is now little over 2 month old since cycled, she was introduced around 4 weeks ago and is the last addition. Stocking : 2 guppies ( 1male and 1 female), 3 gold neon tetras, 3 Pygmy cory, 1 Oto cinclus, 2 neo Cardinia shrimp.

 

[JuiceBox52]

Your tank is way overstocked, which causes stress and high ammonia.
The red Gills is a sign of ammonia poisoning. Do a 75% water change

 

[JuiceBox52]

Did you test for ammonia, nitrite and nitrate? If so what were the results?
How often do you do water changes and how much water do you change each time?

 

[agrownupsupposedly]

0 ammonia, but I do have nitrates but at the safe levels as per test strips.

 

[Essjay]

What about nitrite?

What is the actual reading for nitrate? A lot of strips say that 'safe' is far higher than what is now considered safe. The highest 'safe' level of nitrate is 20 ppm.

Strips usually include a GH test - can you tell us the reading for GH please? I ask because you have soft water fish and hard water fish, and if your water is very soft the guppies will be stressed and get sick easier.

 

[agrownupsupposedly]

She’s no more. Sigh

Nitrates seemed to be between 20-40. I did remove some plants to address the hair algae problem, that might have caused it. I guess I need to be more frequent in partial water changes till the plants takes over and less frequent in feeding. I still wonder why it affected one fish and not the others though.

By the way, GH indicates hard water, the water is generally hard where I live.

Thanks y’all for the replies.

 

[JuiceBox52]

Oh no!