I know you are getting tired of this question but I have tried everything to clear up my cloudy water, half of my fish have died . The store tests my water and it is fine. I change the water, declorinate it. I feed them little, nothing helps. I did rinse the filter in tap water but haven't touched the filter in a long time now. I don't have a whole lot of decor in my tank for the bacteria to cling to, is that it? I am not over populated, if I was, not anymore. I am using sand, am I using too little sand?It's not quite an inch. Please, please help.

Okay, let's try and get to the bottom of this.

I would strongly advise you to buy some test kits yourself. They'll probably cost you a few pennies, but it's worth having them to hand. I really think that testing your water straight from the tank in your own house is much better than taking it on a journey towards the shop. I don't want to upset anyone, but I don't always trust some of these fish shops, they got nothing to lose by telling everything is okay. The problem is, they may be telling you the water is okay when it is not. If that is happening, we won't even think about water conditions and concentrate on other things, if that were the case, we would never get anywhere. So, get yourself an ammonia, nitrite, nitrate and pH kit. Read the instructions are very well indeed. If you don't, you could get false readings. If for some reason you don't want to, or can't get some water test Kit, get them to show you the cards. Ammonia and nitrite should be zero and no higher. Do not let them fob you off if the readings are any different from this. If you have any ammonia nitrite present in your tank water, this could cause cloudy water. The nitrate isn't as critical, you don't really want anything above 40 ppm day.

Now, we need to know how big your tank is and what sort of fish you've got. How often do you feed and how much. What sort of filtration are you using?

What is your cleaning your regime? When you do a water change, how much water do change at one time? How often do you do water changes? Do you keep your filters running all the time?

These are very important questions and you need to answer all of them as best you can.

The amount of sand is unlikely to be a factor. Can you see and area anywhere where the cloudy water seems to be coming from? Maybe something in you filter is bad. Hard to say, I don't have enough information. For now, do some big water changes, maybe that will clear it up.

This happended to me a long time ago. This is what I was told

Cloudy water can be caused by a bacterial bloom. The bacteria are too small for your filter to hold. I was advised to get something call filter aid. What is does is makes the small bacteria clump together and then the filter can do its job on it. Within a day of adding the filter aid the tank was clear again. The cause of the bacterial bloom was my overfeeding.

This is just my experience and what I was told but the filter aid did work

Can you describe exactly the set up of your tank ie filtration size of tank what fish you have and how many and any other info that you feel may help to diagnose what is wrong.

I have a 40 gal tank with 3 2in goldfish, 1 2in plecostomus, and 1 3in kuli loach. It does not say what kind of filter it is, but it's one of those that sits on the side and has two sides, I get blue filters for it, and I recently cleaned it all out too, not the filters this time, keep it running all the time. I usually feed in the morning and at night, just a pinch of pellets and they eat it all. I did one third water changes, when the water did not clear up, then bigger ones, like once a week. The water never looks clear at all, even after water changes, like cloudy lake water, not white cloudy like when you first start a tank. New filter, old filter does not make a difference. I got an extra filter bag to put behind the filters and filled it with carbon and zeolite crystals, made no difference.
Thanks guys.

Okay, so it's not white cloudy water? Umm.... interesting. You haven't got bog wood in the tank have you? That doesn't exactly cloud the water, but it can make you a different colour.

We need to know ammonia and nitrite readings. I know that you said the shop said they are okay, unfortunately that doesn't really help.

Goldfish can be quite messy. However, your Goldfish aren't very big at the moment. How long has it been since you cleaned the filtration? You have to remember that if you were to kill off all the bacteria, it would take another six weeks for them to establish themselves properly. Lots of people just don't understand what the filtration actually does. They take the media out, rinse under their tap water and then wonder why they have problems. You have to treat your media very kindly indeed.

Okay, this is what I think you should try for the next two weeks. Feed your fish every other day but only once. Do a 25% water change once a week making sure that you use a water conditioner. Don't touch of filtration at all. Don't do any gravel cleaning at all. After two weeks, let's see if the water has cleared up at all. However, we really do need to know if there's any ammonia or nitrite present in the water.

Exactly what do you mean by cloudy like a lake? It the water green? Is it dirty looking? (like muddy brown?) If it's green you've got waterborne algae. That's tough stuff to treat. If it's muddy brown, there are many things you can buy to clot the dirt and get it to stick in your filter. However, neither dirt in the water or waterborne algae present any real health risk to your fish so I doubt that either of these should be you issues because you've been losing fish. Just throwing out a couple possibilities.

Now I'm just thinking outloud, but it you currently have a waterborne algae problem, (which can start as sort of a dingy greyish color) you would have to have a considerable amount of nitrate in you water to get it started. That nitrate could be evidence of a past spike in ammonia and the subsequent nitrite. Those could have certainly killed fish.