Ammonia

• Ammonia, a toxic chemical composed of nitrogen and hydrogen, is one of the most common causes of problems in aquarium. Decomposition of organic matter like food and shed fish scales is a frequent source of ammonia, and ammonia problems are more common in aquariums with high pH levels. Fish affected by ammonia poisoning will exhibit hyperactive and chaotic behavior. The fins may appear frayed or show black spots. Some fish may drop to the bottom of the tank and become completely lethargic.
  
  

Aquarium Environment

• High pH can encourage the growth of toxic substances that can harm fish. Slimy substances in aquariums, including slimy water clouds and slime deposits on tank ornaments, are common symptoms of high pH. Sudden algae growth can also be an indication of a change in aquarium pH.
  
  

Respiratory Problems

• Highly alkaline tanks frequently cause respiratory problems for fish. If the fish hover near the water's surface, they may be gasping for oxygen. Discharge around the mouth and gills, as well as a frequent opening of the mouth, may also indicate the fish has pH-induced respiratory problems.
  
  

Disease

• Ich, a common skin infection, is occasionally caused by high pH levels. Some fungi also develop on fish fins as a result of inappropriate pH. Look for fuzzy growths along fish fins and bodies.
  
  

Rapid PH Changes

• The most serious cause of illness is a rapid change in aquarium pH. If aquarium pH levels are too high, it must be lowered over the course of several weeks or months. Newly introduced fish that suddenly die are often victims of shock from pH changes. A quick change in an established aquarium may cause the residents to stop eating, develop illnesses, or experience organ failure.