Cardinal Tetra lost colour

[keehoe]

Hi, anyone have any idea under what circumstance tetra would lost its colour in the day time. But gain back once i turn the aquarium light on.
All my cherry seems don't like the water there also.

I am having a planted tank with DIY CO2 system.

[stormhawk]

Tetras can change colour into a lighter shade to blend in with the surroundings when the lights are off or when it is shaded. This is clearly seen in Beckford's Pencilfish aka Nannostomus beckfordi. In normal colouration it has a stripe running along the length of its body.

In darkness or at night, the fish changes into a blotched pattern on the sides, with the main stripe very very light in colour. This is to confuse predators who feed on them while they sleep.

If the tetra is stressed, that too, can cause them to lose colour. Cardinals are sensitive to pollutants in the water I think, just like Rummynose Tetras. It would be better for you to state the water parameters in detail.

[keehoe]

I think (using Tetra Test Kid) i having low NO3, NO2 (10,1)
GH > 10d, KH = 6d, PH = 7.2

My plant growth 4 inch in one week. (water sprite). Other plant also growing in noticable difference after i added CO2.