Tank Stability in the Saltwater Aquarium

A gentleman by the name of Steve wrote to me recently with the following problem:

MY WIFE AND I HAVE A 65 GALLON TANK THAT HAS BEEN ESTABLISHED FOR OVER 14 MONTHS AND RECCENTLY WE HAVE BEEN HAVING BIG PROBLEMS WITH THE WATER---WE USE A MAGNUM 350 WITH THE POLISHING FILTER (PAPER STYLE)--AND ALSO USE A CASCADE 3 STAGE FILTER SYSTEM WE USE CULLIGAN WATER BUT THIS WEEK AFTER THE WATER CHANGE ONLY 2 DAYS AGO 20% CHANGE AND CLEANED AND RENEW THE FILTERS LIKE ALWAYS BUT THE WATER IS VERY CLOUDY AND GETTING WORSE---8 WEEKS AGO WE TREATED FOR BACTERIA INFECTION THIS TOOK 5 DAYS AND THEN BUSINESS LIKE NORMAL--THE TREATMENT HELP A LOT WE THOUGHT THE WATER LOOKED BETTER THAN BEFORE BUT NOW LIKE I SAID THE WATER IS GETTING CLOUDY AND ALL THE TESTS ARE AT NORMAL LEVELS--WHAT AM I DOING WRONG--ANY INPUT WOULD BE GREAT

I thought I would share Steve’s question as an opportunity to speak broadly on the topic of troubleshooting tank problems and touching on my favorite topic—tank stability. When we start a marine tank, we are attempting to replicate a slice of the ocean. If we appreciate that the ocean is a remarkably stable environment, then we can also appreciate that maintaining stability in the home aquarium is critical to success. Likewise, a change in stability often results in problems—perhaps like the problem Steve describes.

To begin, I am a firm believer that a marine tank really needs a full year to stabilize and begin performing as the aquarist originally intended. Because Steve’s 65-gallon tank is 14 months old, his sudden change in water quality is of even greater concern to me than if his tank was only four months old.

Whenever something goes wrong in one of my tanks, the first thing I do is check my parameters—especially nitrates, phosphates and pH. Steve did check his parameters, and he reports that all his parameters are normal, although I’d like to know which parameters he tested.

If water testing does not help me pinpoint a water quality issue such as Steve describes, then my next course of action is to work back through my husbandry to the last thing I did that was unusual.  For example, did I recently add a new animal? Did I begin dosing a supplement? Did I change my filtration system? Did I (as is the case with Steve) treat the tank for a specific problem?

Steve says he treated for a bacteria infection two months ago, and this is where I would probably begin my line of questioning. What was the bacteria infection? What did Steve use to treat it? It does seem strange to me, however, that the water quality improved following the treatment.

If I were in Steve’s shoes, I would do the following:

• Continue to monitor the water parameters daily (at the same time each day) and record the results so he can see any trends over time.

• Review the tank’s bioload. How many animals are in the system? Is the tank overstocked? Are there compatibility issues that may be affecting water quality? Is the filtration system sufficient for the current bioload?

• Observe any changes in the animals’ behavior. Are fishes “gasping” or “breathing hard”? Are the fishes active? Are they acting normally based on previous observations? Are corals inflated and feeding, or are the polyps retracted?

• Review the tank’s regular maintenance schedule and husbandry practices. For example, is Steve changing out all the filtration media at once? If so, this can cause a major disruption in water stability, and a simple change in tank maintenance protocol may be the ticket. Alternatively, did Steve start using a new food like a liquid food for filter feeders to feed a newly added coral specimen? If so, a change in feeding frequency, amount or brand may solve the problem.

In terms of proactive actions, a series of water changes would be my first choice. I would mix up a large batch of saltwater and allow it to age for at least 24 hours and then begin a series of major water changes over a series of days making sure that pH, salinity and temperature match the tank’s parameters.

In general, our saltwater tanks are a microcosm of the world’s oceans, which are a remarkably stable environment. Stability in our aquaria is the Holy Grail, and we need to realize that EVERYTHING we do to our microcosm can affect that stability. The problems we experience with water quality are often the direct result of a disruption in stability, and that disruption is often a direct result of something—chemical or biological—that we added to or subtracted from the system. Identifying the culprit is often the first step to resolving the issue and re-establishing stability.