You are here:

Fish/Water Clarity - Green


QUESTION: I have a 40 Gal tank that I have one large gold fish and a small comet.  Have maintained and had no issues until recently.  Turned completely green.  Did a massive water change, 80%, which resulted in no change.  Had the water tested and levels are fine.  Was told that my light was probably bad (~4-5 years old) and to turn it off and to add Seachem Clarity Water Clarifier.  It has been 3 days and it made only a very slight difference.  Just not sure what to do now except to take the tank completely down and start over.  Gold fish is large and I'm afraid of stressing him out with a move.  Any suggestion?

ANSWER: How long do you leave on the lighting and do you have your tank near a lot of sunlight or a window? Tanklights at most should be left on for only 6-7 hours to prevent algae growth. You should also check the lighting wattage. It may just be too bright for tank standards.

---------- FOLLOW-UP ----------

QUESTION: Tank is situation by a window but not directly in front.  12 hour cycles with the light.  Same cycle and location for 5 years.  Have stopped using the light as suggested by the clerk at the store when I treated the tank with Clarity and can continue without it, if that is necessary to keep this from ever happening again.  Need to some help getting rid of the green invasion.  So confused over the inability to dilute it out.  Never seen anything like this.

Lower your lighting period and perhaps put thicker blinds and keep them closed if the sunlight is strong. Sunlight is steroids to algae.

I would get a Rubbermaid tub that is large enough to house the two fish (those clear plastic bins), put new declorinated water in the tub, add the filter and let it run for an hour. Put the fish in.

I would empty the tank, scrub everything with a diluted bleach mix (10-15% bleach) as bleach kills the algae spores. Do not use soap. Use a razor to get rid of the algae on the glass. Scrub everything down with the bleach solution. Sit it out in the sun to dry out the bleach.

Refill it, take the filter off the Rubbermaid and remove the carbon pack of the power filter. (If you have a canister tell me so I can give you different instructions) Wash the filter with this bleach dilution. Everything except the carbon package. Get the filter running with the carbon pack on the refreshed tank. Run for an hour and put the goldies back in.

(By the way you will be needing a much larger tank in the future for the two goldfish)


All Answers

Answers by Expert:

Ask Experts


Ash WolFF


My knowledge of fish ranges from freshwater and saltwater fish compatibility and care from easy livebearers to monster fish. I can help you set up a simple freshwater aquarium to a complicated reef tank. I would be pleased to assist anyone who is new to the aquarium hobby.


I have been in the aquarium hobby for eight years mostly dealing with large and small aquariums. I keep mostly monster fish (Arowana's, Large Cichlids; Oscars, and freshwater/saltwater eels specifically) but now that I am in college I am keeping a 30 gallon tropical community and a 45 gallon brackish aquarium while my father tends to the big monsters I left behind.

I'm on YouTube! My 30 gallon community posts are the only ones that are up so far. My Brackish tank is next! I'm on Yahoo Answers:

I am currently in college aiming for a job in Marine Biology.

©2016 All rights reserved.