Clown Killi color fading

I've been looking for a clown killie fish for months and was finally able to grab the last one in the tank from a local shop a few weeks ago. he has seemed very happy and healthy so far but I have noticed over the last week or so that his color will sometimes seem very faded and he will look almost translucent in the light. water parameters are pH 7.4 0 nitrites/ammonia and nitrates of 0-5. I have lots of water sprite floating on the surface for color and I feed him twice a day mixing high quality flakes and frozen blood worms. the last day or two he seems to have a bit of a decreased appetite he is not as aggressive in his feeding where he used to absolutely attack the food. I have seen no other symptoms but I have heard stories of killis dying of apparently no reason before so am a bit nervous. could he be depressed without any females?

 

What time of day is it like this? Do you have a light background and substrate?

 

I usually notice it in the morning. I feed at about 730 am and 730 pm. Background is scenery of plants and rocks substrate is smooth tan aquarium gravel.

 

That's because fish turn lighter at night, they're just coloring up in the morning.

 

hmm I did not know that. very interesting. he still doesn't seem as enthusiastic about food lately. especially the flakes. maybe his growth is starting to slow down and he is not as hungry all the time now? I'll try feeding just once a day for a lil while and see how it goes. thanks for your input.

he had no reaction at all to either flakes or blood worms tonight. seems kind of lethargic. He used to go crazy for anything I dropped in the tank. I'm getting a lil worried. there are no other symptoms.