Aquarium is completely green

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emory7

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Jul 21, 2006
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I've had this fish tank for close to a year, and no matter what I do, I can't keep it clean. It is a 30 gallon freshwater setup with a TOP FIN 3.0 filter system. I have three small fish in the tank, some gravel, and a couple of plastic plants. Every few weeks I have to change out ALL the water in the tank and replace it with fresh water. Also, I generally clean the tank during the process, as well as change out the biological filter. It then takes only 3-4 days for the tank to start getting murky. I've tried to keep it clean afterwards by doing 20% water changes a couple times a week, but the tank continues to grow murkier. 2-3 weeks after a complete water change, the entire tank is green and I can only see the fish if they are up against the glass.

I don't know how to fix this. I only feed my fish once a day, which consists of around 10-12 flakes, and I have cut back the lighting from 12 hours to around 10.5 to give the algae less time to grow. I am beginning to think something is wrong with the filter system. Please help.

If you have no other advice, could you please suggest a good filter system that is somewhat affordable? Thanks for the help.
 
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I get rid of the old filter and carbon, rinse the plastic part, then add a new filter and carbon, close it, shake the filter so the carbon is dispersed, run through water to rid of carbon dust, and then replace in the filter system.
 
Since you have no live plants, you don't need to leave the lights on for 10+hrs. Leaving the lights on for several hours will lead to algae problems, which green water is.

Don't change the biological filter. You can rinse them out but replacing them is bad. Bacterias living in the biologocial filters is what removes the ammonia and nitrites. It would be interesting to see what your ammonia and nitrite levels are, which may be in excess and leading to the algae problems.

Water changes will not fix green water since the algae spores are already present in the water and reproduce given enough light and nutrients (ammonia, nitrates, phosphates, etc). You have a couple of options to tackle the problem immediately.

The cheapest way to fight green water is to starve the algae by completely blocking out light from the tank with a blackout period. Cover the tank so no light gets in and leave the lights off for at least 3 days. After 3-5 days, do a large water change (50%). Still reduce the light period because you'll run into it again eventually if you leave the lights on for over 8 hrs.

Another option is to run a diatom filter, which is a filter that can trap very tiny particles including the algae.

Last option is to use a UV sterilizer, which are expensive but the simplest and most convenient out of the 3.
 
Thanks for the helpful reply phanmc. Given my situation, I will probably try to go with the first option. I gotta tell you, this tank is really green: whenever I change out the water I also have to clean the tubing of the filter system with a brush, since it is usually pretty caked with algae. Will all this caked algae die too (if even alive) in this process? Also, will I need to move my fish, or will they be alright during the blackout? Thanks again for your help.
 
You do not need to move the fish on a black out. Another option is to find some of the snails that come with live plants. Most people find them to be unwanted guests in a tank but I like them. I have found some (about 15) and put them in my sons 5 gal tank that was turning very green. In 24 hours they had cleared all the walls and were working on the fake plants. I no longer have to clean algae from that tank.
 
Just a minute ago I purchased a small UV sterilizer online that I found for cheap. Hopefully this will do the trick. Thanks for all the help.
 
Another way of preventing the algae from properly photosynthesizing would be to turn off the light for several hours in the middle of the day, each day, as opposed to on consecutive days. That is a good option for those with live plants since live plants will be fine as long as the total amoutn of light each day is enough, but the algae on the other hand are slower to begin photosynthesizing, so it will mess up their cycle.
 
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