Aquarium Plants

There are several possible causes and answers as to what is and what caused your cloudy/green water and each depends on differing circumstances. I'll outline each cause and you can evaluate which applies to your situation.

1) Failure to wash the substrate properly. Some substrate materials like Flourite, Laterite, and Sand have lots of dust and "fines". Fines are small particles larger than dust. This cloudy water is usually white to brown in color. If some of these substrate materials aren't thoroughly washed prior to use they will cloud your water until the dust and fines are mechanically filtered out. Filter floss needs to be added to your filter and changed frequently until the water clears...water changes will help too, provided you don't stir the substrate. Also gravel vacuuming the top of the substrate will help remove the "settled dust".

2) Bacteria bloom. For a variety of reasons a tank can experience a bloom in bacteria. While rarely problematic it is annoying. Bacteria blooms are cloudy and white in color AND, this is really important, the cloudy appearance is the same throughout the day. If the cloudy appearance worsens during the day under lights it is an algae bloom even though it may not look green. Most bacteria blooms last for no more than 10-14 days maximum. Any cloudy water that remains longer than two weeks is likely to be free floating algae. Bacteria blooms will end naturally on their own and are usually caused by overfeeding or organic decay from food, dead fish, snails, or plants.

3) Heavy free floating organic particulate. This is water that is basically not clear. If it's yellow in color it could be from the tannins in driftwood or the buildup of organic waste from the plants and fish. It appears in varying degrees of cloudiness. The best way to combat this is with diatom filtering, micron filtering, or by adding high quality activated carbon or synthetic resins such as Purigen to your filter. Routine water changes go a long way in controlling organic pollution.

4) Green water...algae bloom. This is the most common problem if the cloudy situation extends beyond 10-14 days. Note that "green water" is not always green in appearance! Since green water is the most common problem and the most difficult to solve the answer needs to reflect several options. The situation that causes GW (Green Water) is usually a combination of high nitrates, phosphates, and mixed in some ammonia/ammonium. Substrate disturbance is usually the culprit. Water changes alone will usually not rid a tank of GW. Nutrients can be reduced very low in GW and fairly quickly by the GW algaes, but they can scavenge other nutrients...iron and trace elements. So, it's very common for the GW to solve the situation that causes it to begin with, but that won't eliminate the GW. Five methods exist to eliminate GW. Blackout, Diatom Filtering, UV Sterilization, Live Daphnia, and Chemical algaecides/flocculents. The first four cause no harm to fish, the fifth one does.

Method No. 1
The blackout method. Turn off CO2 and add an airstone if available. Your fish and plants will be fine during this short period of time. When doing a blackout follow this procedure exactly.

Day one.

1) Feed your fish. Wait one hour, then do a 50% water change.

Also day one.

2) Cover the tank completely with towels, blankets, or garbage bags so that no light whatsoever gets into the tank...all sides and top must be covered.

Day two.

3) Leave the tank alone...completely alone. Do not change any water, do not feed your fish, and do not even peek to see if the green water is going away during the blackout period. The tank must have complete darkness and no feedings during the blackout period.

Day three.

3) Leave the tank alone...completely alone. Do not change any water, do not feed your fish, and do not even peek to see if the green water is going away during the blackout period. The tank must have complete darkness and no feedings during the blackout period.

Day four.

3) Leave the tank alone...completely alone. Do not change any water, do not feed your fish, and do not even peek to see if the green water is going away during the blackout period. The tank must have complete darkness and no feedings during the blackout period.

Day five.

4) At the end of the blackout period do another 50% water change and lightly feed your fish again. Also address any nutrient deficiencies you may have at this time. Remove the airstone and restart your CO2 injection if using such.

Seven days after day five.

5) Do another 50% water change one week later, then resume you normal water changing routine thereafter.

Method No. 2
Diatom filters can usually be rented from your LFS. This is my preferred method. Personally, I use my Magnum 350 w/Micron Cartridge coated with diatom powder. Diatom filtering removes the algae and doesn't allow it to decay in the tank. You do have to check the filter often, if you have a really bad case of GW the filter can clog pretty quick. Just clean it and start it up again. Crystal clear water usually takes from a few minutes to a couple of hours.

Method No. 3
UV Sterilizers will kill free floating algaes. They also kill free floating parasites and bacteria. They also can be problematic for extended use in a planted tank, as they could cause the “breakdown” of some important nutrients though how much actual effect this has is debateable. They are expensive and don't remove the decaying material from the tank, if you can afford to keep one they are handy to have around, though not as useful IMO as a diatom filter.

Method No. 4
Adding live daphnia to your tank. This can be a bit tricky. First you need to insure that you are not adding other "pests" along with the daphnia. Second, unless you can separate the daphnia from the fish, the fish will likely consume the daphnia before the daphnia can consume all the green water.

Method No. 5
I hate the last way, the flocculents stick to the gills of fish, while not killing them it does compromise their gill function for quite a while leaving them open for other maladies. Make sure when using these "water clarifiers" that your KH is at least 3 degrees...again though not a method I recommend.