I have moved in to a new condo. The only place for the 40 gal. tank is across the room from the picture window (facing north, no sun).

I Am now having a problem with algae that was not present before. The lights are on timer and the feeding schedule is the same as at the old place.

I assume the problem is from the tank being close to the window, has anyone used UV film on the sides of the fish tank?

  • Can you edit your post with a picture of the film? Commented Sep 7, 2017 at 13:58
  • This is my second day have not figured how to post pictures. The film is like thick saran wrap. Maybe Mylar. comes in different shades of gray, many widths, and percentages of UV light it blocks. I was given some that blocks 90 % UV light. You would clean the glass, spray lightly with water or window cleaner, place film on glass and squeegee out the bubbles. It like looking through tinted glass Commented Sep 7, 2017 at 19:17
  • It's really useful to see an image, then people will be able to help you much better. Figuring out how to post images takes much less than two days... Commented Sep 7, 2017 at 20:55
  • What general type of lights (Fluorescent lamp, leds, something else) (and eventually the specific type) are you using? Are you informed about their changing schedule and are you on that schedule? Which type of filtration are you using. What are the values for PH, nitrite, nitrate and phosphate? Commented Sep 7, 2017 at 21:04

2 Answers 2


I have experienced this one before around 3 years ago, I have a 20-gallon planted tank at my desk near the window and was not directly exposed to the sunlight. Days passed by, it produces algae but the colour is green and not brown but I know it is algae because the plants I added in my tank is just Java ferns, Anubias and I forgot the other names of the plant.

There are many types of algae. There are also a few organisms that look like algae but are not algae at all. In a healthy aquarium, the algae will be green, and if left alone, will grow hair-like in appearance. Algae that is red or brown may indicate a water quality problem, such as high dissolved nitrate or phosphate levels in the water. Red and brown algae are also common in new tanks when the aquarium is not yet ecologically balanced.

Sometimes, it looks really good to have algae but sometimes it's not because it grows and spread very fast. So what I did is I clean it up and transfer to another place that won't exposed by any light that came from the sun. I just used a 40watts light for my tank. Tried observing it for a day or 2 and a week after, I didn't see any algae in my tank anymore.

This is the picture before I clean my tank but I think I have deleted my pic after I clean my tank.

enter image description here


Put some plants in it ; they out compete most algae for nutrients.I went to some effort to get a tank up to a skylight for maximum sun ( with plants). Hornwort ( ceratophyllm ( sp.)) is a very easy floater.

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