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Saltwater Aquarium Water Quality Problems
Saltwater organisms require precise water chemistry and quality to survive and remain in good health. And because the majority of the saltwater fish and invertebrates come from the tropical coral reef—one of the most stable environments on earth—their water chemistry and quality must be clean and stable within acceptable ranges as well.
Salinity Problems
Several factors can conspire to raise or lower the specific gravity range in your tank from the ideal reading mentioned earlier.
Evaporation
When water evaporates from a saltwater aquarium, all
the salt dissolved in the water gets left behind and only the pure, fresh water evaporates. The more evaporation that occurs, the higher the specific gravity in the aquarium will rise.
To compensate for evaporation, top off your aquarium with purified fresh water every day. Make sure that the volume of the top-off water exactly matches the volume of water lost to evaporation, however, because you’ll either lower the specific gravity below the target value by adding too much or fail to reach the target by adding too little.
Salt Creep
A small amount of salt will exit the system through a process known as salt creep, thus lowering your specific gravity over time. Salt creep is a crusty buildup of salt that develops on any aquarium or equipment surface exposed to both air and saltwater spray (such as that caused by filter returns, powerheads, or bubbling airstones).
To counteract the effect of salt creep, you may need to add a small amount of aquarium salt to your system occasionally. Simply dissolve the salt in your purified top-
off water, and drip it slowly into your tank or sump. Alternatively, over the course of several water changes, you can mix your replacement water to a slightly higher-than-normal specific gravity, which will gradually bring the specific
gravity of your aquarium back to the desired level.
Saltwater Mixing
A common cause of fluctuating specific gravity is replacing aquarium water removed during a partial water change with water of a lower or higher specific gravity. In some instances this is due to carelessness, but more often than not it’s a result of impatience.
If you mix a batch of salt water and immediately take a hydrometer reading to determine specific gravity, it’s unlikely that you’ll get an accurate measurement. Give the salt time to dissolve completely before you get a reading. Wait approximately 24 hours while circulating and aerating the water with a powerhead or an airstone. Then, test again and add either more salt or more fresh water, if necessary, before performing the water change.
pH Problems
The pH of your aquarium water is another important parameter you must monitor and work to keep stable. The preferred pH range for a saltwater aquarium is 8.2–8.4, which is slightly basic (rather than acidic). The following are some of the reasons why your aquarium’s pH might fluctuate and what you can do to maintain the proper level in your tank.
Bioload
An overstocked, overfed tank is much more prone to a falling pH than one with an appropriate bioload. Excessive acids produced through waste material, metabolic processes of the fish, and rotting, uneaten food in the tank can all contribute to a change in pH. Stock and feed your fish lightly to prevent this problem.
Insufficient Aeration
Carbon dioxide, which is acidic and lowers pH in aquarium water, can accumulate in tanks that lack sufficient aeration and water circulation. This is especially problematic in taller tanks, which tend to have a poor water-volume-to-surface-area ratio and don’t allow adequate gas exchange at the surface. The following tips will help you maximize aeration in your tank:
- Choose a long, horizontal tank with a large surface area.
- Use filter return hoses and/or powerheads to create turbulence at the water surface.
- Use submerged powerheads to circulate oxygenated water throughout the entire tank.
- Include a protein skimmer in your tank. A protein skimmer mixes air and water to create bubbles. These bubbles rise through a cylinder through which the water pumps. Contaminants in the water stick to these bubbles and rise up the column into a collection cup that sits at the top of the cylinder, while the cleansed water returns to the tank. This is an essential water-purification device that no saltwater aquarium should be without.
Overdue Water Change
Even in an appropriately stocked aquarium, the pH will gradually trend downward if you don’t perform routine partial water changes. Change at least 20% of your aquarium’s water volume every week.
Temperature Problems
A temperature range of 75–80°F (24–27°C) is ideal for saltwater fish, but many factors can influence the temperature of your aquarium water, causing it to rise above or fall below your chosen setting. The biggest problems with these temperature swings tend to arise in regions that experience significant air temperature changes from one season to the next, but several other factors unrelated to seasonal change can come into play as well.
Heater Malfunction
The first possibility to consider if you experience a temperature problem in your tank is whether your heater is malfunctioning. The indicator light on the heater can help determine if this is the case. If the air temperature in
your aquarium room is lower than the temperature at
which you’ve set your thermostat, the light should be cycling on and off as the heater works to maintain the desired temperature.
If the light isn’t turning on at all, either the heater is malfunctioning or you’ve set the thermostat too low. If the indicator light stays on all the time, your heater may be broken or too small for the size of your aquarium.
Environment Outside the Tank
The temperature of the room in which you keep your aquarium can have a dramatic effect on the temperature of the water in the tank. For example, if your home has central air conditioning, the fluctuating air temperature can result in a fluctuating water temperature. You can adjust the setting on your air conditioner’s thermostat to minimize this problem.
If your aquarium sits near a window, the temperature can rise and fall during the course of the day as the sun changes position. A window that wasn’t letting in much sunlight when you set up your tank may actually bathe the tank in sunlight at some other point during the day, thus increasing the water temperature. Prevent this issue by placing the aquarium either away from a window or by covering the window with curtains, drapes, blinds, or a shade.
Heater Suitability
For an aquarium heater to do its job properly, it must be of the correct wattage for the size of your aquarium. If the wattage is too low, the heater will constantly struggle to maintain the set temperature or fall short of reaching it when the ambient air temperature is relatively low. On the other hand, if the wattage is too high, the temperature in the tank will always be too warm.
It’s usually easy to determine the proper wattage for any given size of aquarium. Manufacturers usually include this information on their product packaging. If your heater’s manufacturer didn’t provide this information, 3–5 watts per gallon (3.8 L) of aquarium water is a suitable estimate.
| Text & Photos Copyright © 2007 TFH Publications, Inc. | Acknowledgments & Disclaimer |
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