Things You'll Need
- Water sample
Instructions
Look for fish breathing at the surface. Overcrowded tanks do not have enough oxygen and fish may try to breathe atmospheric air to compensate.
Look for fish fighting. Some species become aggressive if they do not have enough space. Look for fish pecking at each other or fish with bits missing from their fins.
Look for dead fish. Overcrowded fish may kill one another. Overcrowding also leads to problems like parasites, lack of food and lack of oxygen. All of these situations can be deadly.
Measure your fish. If your fish won't grow, they could be underfed and overcrowded.
Look for brackish water. If your tank is constantly dirty, you have too many fish. Overcrowding can overwhelm your filter and your pump.
Take a sample of your aquarium water to your local aquarium store and have the chemistry tested. A healthy tank should have zero ammonia and nitrite, low nitrate, high dissolved oxygen and a stable pH.