The ABCs of Water Quality for the Saltwater Aquarium

Every marine aquarist knows that good water quality is a good thing in a saltwater aquarium, but what is good water quality? Good water quality is, generally speaking, water quality that is similar to or better than the environment from which the animals you keep originate. While there may be some variations based on what specific biotope you are recreating, there are about seven parameters which should be pretty consistent across all saltwater aquaria. They are:

• pH

• Temperature

• Specific Gravity

• Dissolved Oxygen

• Ammonium/Ammonia

• Nitrite

• Nitrate

Does Every Aquarist Need to Test for All Seven Parameters Every Day?

Every marine aquarist should know how to measure these seven parameters. Does that mean that every marine aquarist needs to test daily for these parameters? Absolutely not. The more experienced an aquarist becomes, the more he or she will understand the interrelated nature of these parameters. As such, the experienced aquarist, for example, will pay attention to an upward or downward trend in pH and be able to make an educated guess as to what is causing it. Likewise, the advanced aquarist will notice subtle changes in the tank (e.g., increased algae growth) and immediately have a hunch as to what parameter is out of whack. My advice? Test frequently when you are starting out in the hobby, and decrease the frequency of testing as you gain experience. Having said this, I suggest every aquarist should be very aware of any daily shifts in temperature, pH or specific gravity.

Target Values for Optimal Water Quality in a Tropical Saltwater Aquarium

So what values denote good water quality in the marine aquarium? Before I give specific ranges, allow me to harp on a point I have discussed here numerous times: consistency. To wit: within the specified range, consistency is way more important that hitting a specific number. For example, I say below that pH should remain consistent within a range of 7.9–8.6, but a consistent pH reading of 7.8 will be less stressful for your animals than a fluctuating pH between 7.9 and 8.6. In short, keeping the daily fluctuation in pH to no more than 0.3 is far more important to the health of your animals than hitting the magic 8.1 or 8.2. The same holds true for temperature and specific gravity.

Now that I have made my plug for stability, let’s get to the main attraction—the target values:

• pH: 7.9-8.6 with 8.1-8.2 being ideal

• Temperature: 74-80 degrees F (24-27 degrees C)

• Specific Gravity: 1.023-1.025

• Dissolved Oxygen: Around 6.0 ppm

• Ammonium/Ammonia: 0 ppm

• Nitrite: 0 ppm

• Nitrate: below 5.0 ppm for reef tanks and below 20.0 ppm for fish-only systems

So there you have it—the seven parameters of which you should be aware to assess optimal water quality in your saltwater aquarium. Means to test each parameter exist, and you should have the appropriate test kits and tools on hand. Go test!