pH and Alkalinity

The next two tests aren’t so much chemicals as they are general measurements.  Nonetheless, they are important parameters to keep track of.

The first measurement is pH.  pH is the measure of the acidity of a liquid.  pH is a number between 0 and 14, where 0 represents a very strong acid and 14 represents a very strong base.  a pH of 7 is neutral, or neither acidic nor base.  Fresh water has a pH of 7.  The oceans’ pH averages between 8.2 and 8.4.  If your pH is in that range, you’re in good shape.  If it falls out of that range, you’ll need to correct what ever is wrong with your aquarium – look for dead animals, or possibly over feeding.

Alkalinity represents the ability of the water to neutralize acids.  It can also be thought of as the buffering capacity of the water.  Alkalinity helps the water resist changes to its pH.  I don’t have a good test for alkalinity at the moment.  The test kit I have only offers three ranges – “High”, “Normal”, and “Low”.  Since it sounds better, I’ve been targeting “Normal,” and have yet to seen it move out of that range.  Some day, perhaps I’ll find a good test for alkalinity.

Temperature

Another important measurement is the temperature of the water.  I target 77° Fahrenheit (25° Celsius).  But, anything between 70°F and 82°F (21°C and 28°C) is fine.

A good aquarium heater will keep the temperature up.  but I actually had a lot of trouble this summer keeping the temperature down!  When the temperature in the house is over 85°F all summer long, it’s a little difficult to keep the aquarium under 82°F.  There are aquarium chillers that you can buy, but I choose a less expensive method.  I turned the aquarium into a swamp cooler by blowing a small fan over the surface of the aquarium.  This promoted evaporation, which reduced the temperature of the water.  Of course I had to add replacement water more often than I would have otherwise.

Calcium

Calcium is an important chemical for marine aquariums.  Both marine invertebrates and fish are highly dependent on calcium.  Corals, crabs, shrimp and other marine invertebrates use calcium to develop their exoskeletons.  Fish also need calcium, for their internal skeletons.  So, a healthy level of calcium is important to your pets.  Interestingly, calcium is also a big part of the buffers in saltwater, so it affects alkalinity and pH as well.  If you’re interested in the details of how calcium affects pH and alkalinity, I recommend you read this very good article on calcium in saltwater.  The oceans’ calcium level averages 410 ppm.  This is a good target for marine aquariums as well.  Anything between about 360 ppm and 450 ppm should be fine, however.

Last weekend was the first time that the calcium had ever been tested in my aquarium.  The fish store did the first test, but the results were not exactly what they expected.  They were not expecting a relatively new aquarium, which had never had any calcium added, to have a calcium level of 530 ppm!  They actually did a calcium test a second time just to make sure they hadn’t messed up the first one.  A calcium level of over 550 ppm will actually start to precipitate out of solution, creating an effect kind of like snow.  So, I was very close to a small disaster.

After the fish store employee told my father and I that a calcium level of over 550 ppm is potentially very bad, we decided to get a calcium test kit and try some experiments.  I also carefully read the label of my saltwater mix, and discovered that it has “high calcium and magnesium concentrations.”  I decided that the saltwater mix was a likely suspect, so I purchased another brand of saltwater mix. Then, my father and I tested everything from the RO/DI water that I use to make saltwater, to the aquarium itself.  This is what we found:

Even though the new saltwater mix brand still had a calcium level of 410 ppm, a 20% water change was able to reduce the calcium level dramatically.  I’ll continue this careful testing and water change this weekend, so that I can make sure that the original salt mix was my only problem.  If the calcium level continues to rise without the calcium fortified salt mix, I’ll be looking for other places where the system could be leaching calcium from the substrate or shells.