My mother recently bought a lovely male betta fish after setting up a 10 gallon tank for him. We used a cupfull of gravel from my old tank, along with a well used filter cartridge from my filter that was broken to help the tank cycle more quickly, mom decorated it with some places for him to hide and explore. I may post pictures later if this behavior persists, because it is quite disturbing to me... I have never seen a male betta in a tank develop horizontal stress lines like this.
Anyway, he is a bluish green betta, part of his tail is a pale brownish color with very dark blue tips. HOWEVER at the moment, he keeps truning pale brown (litterally his head changes from an almost black blue to a sickly pale brown color). He keeps hovering around one side of the tank and I'm not sure... is it possible for them to see themselves in the side of a tank?
The only other thing that seems unusual is his reaction to the background... he has been fine in this tank for 3 days now, but the background we got (which has been on the tank since we set it up) was supposed to be a static cling background and now it's sort of bubbling off... he will occasionally cruise along the back of the tank and flare at the background, which is only a green garden-like image. While he is all flared out at the background, his color returns to his normal, blue-green.
If I distract him by gently placing my finger on the glass (as I often do when feeding him) He calms down, and his color returns to normal surprisingly quickly. Once I walk away though he develops the stress lines again.
All the water readings are fine, and he is currently the only fish in this tank. The temperature is about 78F. I'm concerned for the fish because I know that high levels of stress can cause big problems in fish... but I have no idea what's stressing them. As I type this, he just went back to his normal coloration, only to return to the sickly looking brown. I'm thinking of turning the light off for a while, although that will not solve the problem permanently...
Late last night I removed the background and kept his light off a little earlier than usual. This morning he is no longer turning pale brown with the stress lines, and he is no longer flaring at the back of the tank.
However, he is still fascinated with the left side of the tank. He swims aroudnd normally, doesn't seem sluggish, fins aren't clamped, but he will occasionally go down to the front left corner of the tank and put his nose in it so that he's resting almost against the gravel. Then he will resume cruising back and forth with his nose pressed to that side of the tank :\
I think it's a good sign that he is no longer displaying the stress lines or flaring, but the behavior still seems odd and I'm wondering what could have caused it.