cloudy water in a fresh water tank

Question
I have a 30 gallon fresh water tank with neons and guppies.  I use a water conditioner in my tap water for every water change.  I am also doing a water change once a week and am probably removing about 4 gallons each time.  The cloudy water just started about 2 weeks ago, up until them the water was crystal clear.  I have had my tank about a year and this is the first time the water has turned cloudy.  What am I doing wrong?  I do not want to loose any fish.

Answer
Hi Elizabeth,

Neither neons and guppies produce much biological load, so my guess is that something has overwhelmed the beneficial bacteria that keep your aquarium stable - "cycling" has been interrupted in your tank. If this were the case, the cloudy water is called a bacterial bloom.

There are many reasons why this could have happened. You might have over cleaned your aquarium. Doing too thorough a job vacuuming the gravel, replacing/rinsing all of the filter media, and any kind of bleaching to the decor can come together to disrupt the beneficial bacteria that colonize your aquarium. Your filter may have stopped working, for example during a power outage. It only takes a little while for dry filter media to lose all of its beneficial bacteria. Without water continuously passing through the filter media, it soon becomes stagnant and this can cause an interruption in your cycle.

You may have also overfed your fish. Too much uneaten food will eventually decay and overwhelm the filter, especially if your filtration is rather modest. Neons and guppies don't need much filtration, but it is still advisable to have about 4-5 times turnover - in a 30 gallon tank, that means 120 gph or 150 gph...gallons per hour, that is. Check to make sure your filter or filters are putting out that much flow. If they are not, add another filter.

Those are my guesses as to what has gone wrong - now, here are my suggestions for ways in which to fix it. Do a substantial water change, about 50%. Vacuum the gravel if it looks like it is dirty. Any filter media that needs replacing (such as disposable cartridges) should be replaced. Do not rinse biological media (such as bio-wheels, ceramic rings, foam sponges) in anything but aquarium water, or water without chlorine in it...tap water kills beneficial bacteria! The chlorine or chloramine that makes it safe for you to drink, kills the bacteria that keep your aquarium stable and cycled.

Change 25% of the water every day after that for another week or so, or if you prefer change 50% every other day. If you have a test kit, keep checking the levels to make sure all is well. 0 ppm of ammonia and nitrites are a must (an established, healthy tank never registers either of these levels) and nitrates should not be too high, under 20 ppm is preferable. pH, alkalinity and hardness levels ought to be about the same as what your straight tap water tests at.

During this time while the water is cloudy, it is advisable to feed very little, if anything at all. Adding some aeration (via a powerhead at the surface, or an airstone or two powered by an air pump) will make your fish feel more comfortable and might help speed up the process by which your aquarium regains its balance.

I hope those suggestions help! These two websites discuss in depth the concept of cycling, if you are uncertain as to what it entails...and both have suggestions for breaking down aquariums (to redecorate, move them, etc.) and tips for performing routine maintenance safely:

http://freshaquarium.about.com
http://www.firsttankguide.net

Take care! Best of luck to you.
Nicole