My fish Gibbs (pictured to the left) suddenly started flashing some fear stripes. They keep on fading and reappearing in a matter of 5-15 minutes and he keeps staring at something I can't see (I put black paper on two sides of the aquarium to block whatever it was).
Earlier today, I moved him to a 2.5 gallon tank to help with his mild case of fin rot. The water is conditioned and detoxified, the filter was turned off after 2 days (current was too strong). The water is between 77-78 degrees. I don't have the nitrate, nitrite, or ammonia levels (I'm getting a water test at the pet store tomorrow) and pH is 7.8.
Gibbs is a super energetic fish, even with fin rot, and he spent the whole day swimming around exploring and nipping at me whenever my hand hovered close enough. Then all of a sudden, something scared the crap out of him and he wasn't very hyper anymore.
I searched the tank which only has gravel, a leaf hammock, and a silk plant so far, and even listened for any disturbing noises. Nothing seemed out of place. The only thing I could think of was the clicking of the heater. The heater clicking on didn't disturb Gibbs, but when he swam over to it just as it was switching off, he darted away and sported those fear stripes again. The heater is a 50 vte Marineland heater and I heard 50 watts is too much for 2.5 gallons, but it's all I have right now and it keeps the temperature from fluctuating.
Should I unplug the heater overnight? Do heaters send out shockwaves or something when they fail? I really want to avoid unplugging it since my house drops down to 66 F, but I don't want to wake up to a dead fish either...