Green Water

[sezra]

My water keeps going green, it doesnt smell, its just really green. I have a 100l tank which is being filtered by a fluval 305 so filtration isnt an issue.
 
The room it is in is fairly small and gets a lot of sun in the morning, but the tank itself isnt in direct sunlight. I do 25% water changes every week, although for the last month i have been doing 50% water changes in an attempt to clear it up. 
 
I've tried black outs which havent worked and now im at a loss for what else to do.
 
I have no live plants in there, as I dont have a great deal of time for maintenance etc, but I have heard that by adding hornwort, it can help battle the algae. Is there any truth behind this?

 

[Miller2009]

I suffered with the same thing when I upgraded my tank. At first I thought it was just too much light getting into the tank then I twigged on that I was leaving my lights on too long. I tried blackouts like yourself but also found it not to work. So what I was doing was about 40% water change every other day for about a week or so. Since then (touch wood) I ain't had no problems but I only have my lights on for at most about 5 hours a day.

How long do you leave your lights on?

 

[sezra]

Theyre normally on during the day, and then for a few hours when I get home from work so that I can enjoy the tank. Maybe I should increase the water changes? I didnt want to over do it. Did your tank suffer any adverse effects changing the water so often?

 

[levahe]

You could try a 3 day blackout and then a large 75% or more water change, that should help.
Too much light and ammonia spikes can cause green water. It sounds like this tank needs less light.
Increasing the weekly water changes is a good idea too, something like 50% pw. Do you keep the tank clean and do gravel vacs? A build up of organic matter could cause water quality issues along with overfeeding.

 

[sezra]

You could try a 3 day blackout and then a large 75% or more water change, that should help.
Too much light and ammonia spikes can cause green water. It sounds like this tank needs less light.
Increasing the weekly water changes is a good idea too, something like 50% pw. Do you keep the tank clean and do gravel vacs? A build up of organic matter could cause water quality issues along with overfeeding.

 
I do a complete clean every week at the moment. I clean the filter pads (in the tank water), gravel vac and clean ornaments, as well as do  50% water change. Nothing seems to work. The tank isnt overloaded and I have a filter that is more than capable of dealing with a tank this size. The only thing I can think of is light levels, but as i said before, ive had a complete black out for the last 2 weeks.

 

[levahe]

For a blackout to work it needs to be completely black in the tank with no light at all not even taking the cover off to feed fish. Something like draping several thick blankets over the tank (something that allows oxygen to get to the fish) and using string to tie around the outside to ensure no light gets in at all. Even the slightest light will allow the algae to cling on. You need to kill it off. Do that for 3 or 4 days or even a bit longer if you want and the fish will be fine during this period. Then do a massive water change .

 

[sezra]

ok, so I have used some towels to black out the tank. Im kind of worried about restricting oxygenation of the water though. I have a small filter which I use just to break the surface and keep that circulating, so that may help. Are you sure this isnt going to kill the fish?

 

[levahe]

As long as oxygen can get through the towels, it will be fine as long as you don't place too many layers, keep your main filter running that should be ok to circulate the water for gas exchange.
Don't forget to turn the lights off lol !!

 

[sezra]

cool, one last question, how can i prevent algae growth in the future?

 

[levahe]

I would say less light, try 6 hours a day lights on and use a timer to ensure a good routine, also try not to let the tank get too much natural daylight. From what you have put here it seems your tank is well maintained so that only leaves light as the culprit.

 

[levahe]

How did it go OP?