The easiest response is that it could be a reflection of a filter medium that hasn't had enough time to go through the Nitrogen Cycle / develop good bacteria. It is overwhelmed for now and needs to break down ammonia and nitrates, first.

Beyond that, assuming the tanks has been "cycled", it could be overfeeding and/or not enough filtration. Where exactly is your tank and filter at? How big of a tank? What fish do you currently have? What is the temperature (metabolism)?

What kind of tank? Planted? community? Salt? Well water?

Sorry I didn't originally include that info :) I have a 55 gallon, the filter is on the right, it sucks up in the middle and pours out on each side. It is planted, I use tap water, a little salt. The temp is around 81 degrees, and I mostly have tetra's, platy's, some Danio's, 2 bala's, and a rainbow shark. Thanks for helping :) Christy

I would start by changing your charcoal. You would be supprised how much it effects the tank. If that does not work, try a 10-25% water change. Before you do that make sure the tap water is not cloudy. If that doesnt work then get the jungle 6 in one test strips and see what ball park your in on your nitrate, nitrite, chlorene, hardness, alklinity and pH. These strips wont give you exact measurements but will show where your out of the acceptable ranges. I highly recremend this product for any planted tank or tanks with demanding fish. (I do not sell this product, just am a fan if it)

Back to the problem. Another thing I found that helps to clear up a lightly clouded tank is adding bacteria. They have bottles at walmart to your high end fish store. Its about two bucks for the small bottle. Get this and follow the directions. This can help your tank reestablish a bacteria colony if yours got knocked out.

My guess of what is going on is you probably are at the start of a plankton bloom. If you have this go full bloom, its difficult to get rid of. This is when your tank will become pea soup. It wont effect your plants or fish, you just cant see them. I had this happen to my 20 gal planted fresh water tank. I was doing 90% water changes and the bloom would come right back. So I let it sit for about 2 weeks. I bought daphnia and they cleared it up in two days. The fish then ate all the daphnia. It looked like it was going to bloom again, getting cloudy, but not green. I changed the filter cartrage (charcoal) and it cleared the water crystal clear and its been that way for about a month now.

Any way, I just rambled away. I hope this helps you out.

I believe my tank is just starting to cycle. Amonia level is down, nitrites are close to zero, nitrates have risen some but are at a safe level. However, my water has clouded and has a yellowish brown tint (possibly from a piece of driftwood). Will the cloudiness go away on its own? Should I make water changes if the nitate level stays ok?

Once you get past Ammonia & Nitrite, the Nitrates are relatively safe. Hard to say why the tank is cloudy, but at this point you could do a water change - 10% to start - and see what happens.

Sometimes cloudiness is caused by too much neutriants in the water which causes an alge bloom. Most times this is caused by overfeeding or not enough/clogged filtration. Sometimes large amounts of water changes make it worse by adding neutriants. Usually when the tank cycles and becomes balanced this doesn't happen. Sometimes if you change all the filter medium at once it triggers this. Adding a second filter would be a good idea.