Cloudy fish tank

Question
QUESTION: Hello, I've had a 50 gallon fish tank for about 6 years now. Over the last two months I had 5 fish die and my tank has become extremely cloudy. What can be causing this problem? Any suggestions would be extremely helpful.

ANSWER: Hi Nick,
You most likely have some kind of bad bacteria in your tank.  Did you check ammonia, nitrites, and nitrates.  Your ammonia should be zero, your nitrites zero, and nitrates must be low.  Ammonia is the number one killer of fish.  It poisons the water.  It could also be something that is in your tank that is dissolving, a decoration that isn't safe.  It could also be chemicals that was added to your water.  Overcrowding may also be a reason.  Carbon should be changed once a month, and the sponge should be rinsed in water you have removed from the tank, and never rinsed under tap water.  A sponge is full of good bacteria, and if rinsed under the tap, this would kill your good bacteria.  A sponge is good until it is old, ragged, and falling apart.  Check your water, and if you do have ammonia, or nitrites, do water changes everyday to get rid of it.  It could also be food that was left decaying in the gravel, or dead plant roots.
 Sometimes when you cannot find the cause, and your fish are dying, you must start over.  Rinse everything in your tank with warm water until it is clean.  If you have to do this, I would also add a little bleach to the water when cleaning.  Make sure you rinse everything well, and let then fill your tank again, and let it cycle.  This would be the last resort.  Try to find the cause.
I hope this helps.
Lynda

---------- FOLLOW-UP ----------

QUESTION: Thanks, but I have another question. I tested the water and it says that the water is very hard. Could that be causing the water to be cloudy? If not what are the dangers with having hard water. And what can I do to correct this problem.

ANSWER: This could be the reason why your water is cloudy, but you must find what is making your water alkaline.  Do you have sea shells, or coral in your tank?  Alkaline water can kill fish if the fish need acidic, or neutral water or if your water is very very alkaline.  How high is it?   What fish do you have in this tank?  Check to see if you have something in your tank that should not be in your water.  It could be a decoration..also check your tap water to see if it is hard also.  Write back to me with more details please.
Lynda

---------- FOLLOW-UP ----------

QUESTION: I checked the Alkalinity of the fish tank and it is low, but i tested the pH and it says that it is acidic. Also I checked my tap water and it is very hard. I do have sea shells, they have been in my tank for about 15 year, I transferred them into my larger tank, but I have no coral.  

Answer
If your tap water is hard, and you have sea shells in your tank, then your water should be alkaline.  It doesn't make sense to me that your tank water is acidic, unless you are using chemicals to bring down the PH.  Chemicals are poison to water because it makes the water chemistry fluctuate.  If you have African Cichlids, then your water should be alkaline, and not acidic.  I do not know what fish you have in your tank, so cannot tell you more on the water they need.  As for your water being cloudy, the only reasons I can think of are the ones I mentioned to you.
Lynda