But it significantly increases the odds. In this section, we list some of the more common stress-inducing conditions. In all cases, the level of stress induced by a specific factor is highly species-dependent. You should be aware of the type of stress that will be present in your tanks and select fish known to tolerate such conditions well. For example, if your water is hard and alkaline, you're best off selecting fish that thrive under such conditions.
Ammonia is toxic in low concentrations and severely stresses fish under ANY concentration.
Although significantly less toxic than ammonia or nitrite, nitrate also stresses fish. The water temperature of your tank should match the needs of its inhabitants. Keeping water temperature too cold or too warm for a particular species will stress those fish. Some fish prefer soft water, others prefer hard water. Other species are extremely intolerant of salt.