cloudy fish tank

Question
hi. i have a thirty gallon fish tank with only guppies in it. There are 13 guppies in the tank. I have had my fish tank for over a year. i do 25% water changes every week and it still turns a grayish green color again. nothing seems to work. the fish are healthy ..the water doesn't seem to bother them but it is not pleasant to look at. i wanted a fish tank so i could have crystal clear water with beautiful guppies in it. Can you help me?


Answer
Hi Anthony,

Green water is the result of an algae bloom. The form of algae you are experiencing is suspended in water, yet is too fine to be trapped by the filter. Algae is common in aquariums, but an excess of algae can be prevented. Fortunately, algae is not harmful to fish. You can do the following to remove the problem:

-Perform a 20% daily water change for 1 week, or until the problem clears up
-Keep aquarium lights on for no more than 8 hours (unless you have live plants)
-If you have live plants, keep your light on for 10 hours until it clears
-Keep doing weekly water changes to maintain water quality and remove nitrates
-Remove the aquarium from any potential source of sunlight

If you do not have live plants, you can cover the aquarium with dark towel(s) for 3-5 days. This will effectively starve the algae of light, killing it. This will ONLY work if you do NOT have live plants!

If you have live plants in the tank, keep the light on for no more than 10 hours until the problem resolves.

After you have killed off all the algae, you can put some live plants into the tank (if you have not already). The Plants will make your aquarium look much nicer, and they will out-compete the algae for nutrients, reducing algae greatly.

Good Luck, and Happy Fishkeeping!