Sudden fish death

Question
I do a water change once a month and i empty out over halo the tank. Plus i vaccum the gravel to make sure its clean. Believe it or not, the ph of my tap water is a perfect 7.0. Odd huh? I don't have a filter to clean. See the filteration is built into the back of the tank. It has bio balls and i have to buy charcol bags to stick down in the back of the tank. My biggest fish is aboout 2 inches. The rest are smaller. I feed them blood worms, brine shrimp, and flake food. (Not all together). They usually eat the fodd pretty quickly. Sometimes it may take a couple of minutes for them to eat what is left on the bottom. I feed them once a day, at night. My temperature is always at 80 degrees. I hope this helps. Thanks again, Tara.--
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Followup To
Question -
Hi, how are you? I have a 65 gal. tank. My fish were doing good a couple of days ago, and then all of a sudden they are starting to die. I have no ammonia and my ph is about a 6.2. My ph has always been low, i dont know why. No matter what chemical i use to raise it , it simply dosent work. My filter system is built into the back of the tank. The tank is probally 10 years old, but it has only be set up for 6 months. I had golden sharks and tetras. They all died. I have a few bala sharks, a leaf fish, catfish, and a couple parrots. I dont understand why they are dying. My water is constantly cloudy no matter how many times I do a water change. Any suggestions? I appreciate your time. Thanks,Tara.
Answer -
Hi Tara;

How often do you make water changes?
How much water do you replace?
Do you vacuum the gravel?
What is the pH of your tap water?
How often do you clean the filter?
How big are the fish?
What kind of fish food do you use?
How long does it take the fish to eat all the food from everywhere after you put some in?
How often do you feed them?
What is the water temperature?

Let me know as soon as you can......

Chris Robbins


Answer
Hi Tara;

It may be that there isn't enough oxygen in the system. I have found that trickle filters or wet/dry systems (like yours appears to be) often don't provide enough surface agitation (water movement at the top of the water) to keep the system healthy. Is it pumping water through the balls and charcoal okay?

Try using an air pump to provide bubbles in the water with an air stone. I have tried this on many chronically cloudy tanks that have low pH and it fixes them right up within a week or so. The pH rises and it clears up. The bubbles look nice too.

Altering the pH will cause cloudiness too. Products that raise the pH have dissolved minerals and they often make the tank look 'milky'. It really is best for the fish to not alter the pH with chemicals at all. Chemicals make the pH fluctuate drastically within hours and that stresses the fish too much. To help keep the pH more stable in a natural way, make more frequent water changes. Replace 25% of it every week instead of 50% every month. Don't vacuum the gravel every time though, only about once a month. This avoids shocking the fish but provides a more stable water chemistry.

Followups welcome.....

Chris Robbins