Do water conditions affect fish compatibility?
Written by
John Williams
Reviewed by
Prof. David Walsh, Ph.D.The most important water conditions, rather than behavior, should be considered when determining fish compatibility. Pairing temperamentally compatible fish with those of widely different needs can result in physiological distress. Tropical fish require water temperatures between 72°F and 82°F (22°C and 28°C), while goldfish prefer water temperatures between 60°F and 70°F (15°C and 21°C). Differences in acidity disrupt vital internal body functions. Differences in hardness affect breeding and immune response.
Temperature Conflicts
- Cold-water species slow metabolism in warm tanks
- Tropical fish develop diseases in cool water
- Maintain separate thermal zones impossible
pH Imbalances
- African cichlids require alkaline pH 7.8-8.5
- Amazon species need acidic pH 6.0-6.8
- Mismatches cause osmoregulatory failure
Hardness Issues
- Livebearers need hard water for breeding
- Soft-water tetras develop swim bladder problems
- Mineral imbalances affect egg development
Osmoregulation failure is when fish are faced with the wrong chemistry of their water. This concerns the internal salt and water balance, and forcing a fish to live at the wrong pH causes it to expend unnecessary energy to prevent further disease. With chronic continued stress, organs begin to break down, and fish stop eating, along with being more prone to disease.
Breeding fails, when they are mismatched in hardness. Guppies require soft, calcium-rich water to develop their fry. In contrast, soft-water species, such as discus, need mineral-poor water to fertilize their eggs. When these pairs exist in the wrong environment, they produce eggs that will never hatch, or fry born deformed. Match hardness to the species' natural environment.
Test your water weekly with reliable kits. Match new fish to your tank's parameters. Acclimate species gently over 90 minutes. Sensitive species need drip methods. Stability is more important than perfect values. A sudden shock disturbs fish more than slight imbalances.
Focus on parameter alignment first, before considering temperament, group fish with the same needs for temperature, pH, and hardness. Suppose a tank is mixed-species, combining fish with similar needs and creating microenvironments with buffering substrates. Before any behavioral observations, always check their compatibility using compatibility charts with materials such as stone, rock, or other buffering substrates.
Read the full article: Fish Compatibility Chart Ultimate Guide
