MURKY water and hurt fish

Question
Hello Nathan-  I have had my tank set up for about 1.5 years in my apartment.  It is a 15 gallon tank with a whisper filter.  In the tank are 3 barbs, 2 silver dollars, one catfish, and one clown loach.  I have never had problems with my tank, but about a week ago the water started becoming cloudy.  VERY cloudy.  I performed a 50% water change, and added new Deer Park Spring water to the tank (5 gallons to be exact). Now, the water is even MORE cloudy to the point where i cannot even SEE the fish in the tank, and my catfish has developed this awful looking wound on his side...it almost looks like a burn!  I have tested the Deer Park water by itself, and it typically comes out within the limits my fish could handle (pH-hardness etc wise).   The i do not have another 'quarantine'tank set up to move the catfish too, as i downsized from my 55gallon to my 15 gallon about 1.5 years ago.  I am nervous that ALL of my fish are doomed, and my poor beautiful catfish..well, he appears to be a goner already.  The water is completely out of whack, the nitrates are off the charts, the pH is low and the i would be very sad to see my tank suddenly go down in flames.  I have absolutely no idea what has caused my tank to suddenly deteriorate, please help.

Answer
Hi Corinne,

Cloudy water can be caused by a multitude of factors, but the most common causes are bacterial bloom, and algae bloom.

Have you done any recent maintenance, changed the type of water used for water changes (from tap water to bottled water, etc.) or made any changes to the aquarium? For example, did you recently change out all the filter media, or moved the tank to another location? These things could have caused your water quality to deteriorate. But let's not worry about the cause; the solution is important.

As you mentioned, the water quality is terrible at the moment. Is 'Deer Park Water' a kind of bottled water? Change another 50% of the water, to control the ammonia, nitrites, and nitrates. Your catfish and other fish are most likely suffering from either chemical burn (from the nitrites, nitrates, ammonia, etc.) or pH burn (low pH), or a combination. Your pH should be around neutral (7).

Perform a large water change every day (25-50%) until the problem resolves. Make sure you use a dechlorinator to reduce stress as well as detoxify your water. Adding a beneficial bacteria booster such as Stress Zyme or Cycle will also prevent ammonia and nitrite levels from skyrocketing. The water changes should also take care of the pH since you mentioned that the water you used was within parameters.

In the future, remember to do weekly 10-25% water changes. Make sure the water does not contain heavy metal ions, silicates, or nitrates.

You can also purchase a water clarifier from your local fish store to help with the cloudiness.

I hope these solutions help - Good Luck, and Happy Fishkeeping!