What Other Variables Besides Temperature Could Affect a Fish?

Sudden or Drastic Variations

• First, it must be noted that fish are sensitive to any drastic or sudden water changes, temperature or otherwise. Many variables are at work in an aquatic environment, and their consistency is essential to fish welfare. A considerable change to any variable, especially when it occurs rapidly, can cause shock and even death. This means your fish can be affected negatively by your attempts to correct a water imbalance just as readily as the original imbalance itself, if you make a major change. Make any and all water adjustments gradually, even over the course of days when necessary.

Aeration

• Oxygenation and circulation, otherwise known as aeration, of aquarium water are important variables. Fish require enough oxygen and low enough levels of carbon dioxide to breathe. Too little oxygen can cause lethargy and even suffocation, while too much can trigger potentially fatal gas bubble disease. Proper aeration also helps ensure all tank water gets filtered and helps prevent algae blooms. Some aeration occurs naturally at the surface of the water, and filter systems provide some, too. Various aerating devices are available commercially.

Water pH

• Water pH refers to the how acidic or basic the water is. Different aquatic life prefer different pH levels; freshwater fish typically need it in the range of 6.5 to 7.5, while saltwater fish generally need a pH above 8.0 and maxed out at 8.4. Measure pH with a testing kit or electronic meter at the same time of day, as it fluctuates over the course of the day. A variation of more than 0.2 in one day can be devastating to your fish, so keep a close eye on pH and learn how to raise and lower it slowly as needed.

Salinity

• If you have a saltwater aquarium, the salt content of the water is a key variable. It's generally talked about in terms of gravity, which is a temperature-dependent reading of salinity. A hydrometer is the standard equipment for quantifying gravity. The target reading is 1.021 and 1.024 for almost all marine systems. Follow the directions on your salt mix carefully, and remember when replacing evaporated water that only the water disappeared, not the salt, so top off with fresh water only.

Nutrients

• Important nutrient compound levels in aquarium water include nitrate, nitrite, phosphate and ammonia. These are given off by waste products and decaying organic matter. Each nutrient has optimal levels somewhat dependent on the types of fish and other life in your tank, though there shouldn't be any ammonia. Readings that are too high can cause illness and lethargy in fish, or even be fatal if it gets bad enough, and lead to algae growth. Also, heavy metals, such as copper, iron, lead, and manganese, can contaminate the water at too high a level. Testing kits are available for nutrients and heavy metals and should be used weekly or bi-weekly.

Other Variables

• General water cleanliness is another variable that can affect fish health and vitality, along with other variables, like nutrient levels. Use a net to remove debris, and a filtration system rated for your tank type and size. Hook up a protein skimmer if you have a saltwater tank, too. Don't overfeed fish and use a substrate vacuum. Monitor alkalinity and calcium levels with testing kits, as well. Research whether your fish have special lighting needs, because if they aren't met, your fish activity levels and health will suffer. Also research which substrate and plants are good for your types of fish and what tankmates they get along with, and how much space they need, since overcrowding can stress them. Additionally, algae growth, bacterial or fungal contamination, parasites, ich, cropsy, lymphocystis and other diseases can break out in a tank and affect your fish. Monitor them for changes in their appearance or behavior, and consult a vet or trusted fish breeder for treatment advice.