New tank, new tankmates, new aquascape = temporary paleness. Returns to color in 1-2 weeks.
White/light substrate makes fish pale to camouflage. Switch to dark substrate for vibrant fish color.
Excessive light bleaches fish over weeks. Reduce photoperiod or intensity.
Color loss precedes visible symptoms by days. Watch for spots, fin damage, lethargy in following days.
Bullied fish lose color from chronic stress. Remove aggressor.
Fish naturally fade as they age past 50% of expected lifespan.
Test water first - many "behavior" issues are actually water-quality problems. Use the water parameter checker to score your test results, the disease symptom matcher if you observe physical signs, or the general diagnoser to narrow further. Browse the disease database if illness is suspected.
Browse all behavior troubleshooting articles.