What does it mean when a fishes scales turn white?

Answer 1

This question is all over answers.com. I'll paste my stock response.

This answer assumes Freshwater Fish. Much of this information is relevant to salt water fish as well.

A fish will begin to turn silver due to bleaching from ammonia poisoning. First its gills will change, then the rest of its body. After the body turns silver, the fish will soon die.

Many websites will tell you to change 20% of the water a week, however, in a chloramine environment this will kill your fish as that compound is a mix of chlorine and ammonia. A healthy freshwater aquarium fish typically wants the following environment:

+ A pH of 6.8

+ A water temperature of 80-84 degrees Fahrenheit

+ 0% ammonia, nitrate, and chlorine

Your tank can handle up to .25% ammonia at a pH of 6.8. The higher your pH, the more toxic your ammonia problem becomes.

The best way to ensure a healthy environment is to promote healthy bacterial growth (cleans the ammonia). You should have adequate filtration and heating with pH conditioned water. There should be a good layer of aquarium sand underneath your decorative gravel; bacteria cannot live in loose rock. If you have algae growth and your ammonia is low, test for phosphates.

If you cannot build a proper tank then use a mineral water (not distilled) or conditioned tap water that has been pre-treated for pH. Never change your pH all at once, drip the water in slowly. You should have a batch of good water ready for any changes you do. Simply adding chloramine treated tap water at a pH of around 7.2 in a 70 degree tank is a fantastic way to kill your fish unless you are topping off a properly filtered ecosystem. In that case the bacterial colonies will quickly dispose of the toxins.

The silver color is a hint.

**This answer was written with a common betta fish tank in mind. You should look up the pH tolerances for your specific environment before following these suggestions.