Green water - help!

[ZombieGirl]

Hello all. I have a 36 gallon freshwater tank with 2 Japanese goldfish and a pleco (I know some people are against having plecos with GF but they've been fine for months now). After a recent water change, my water became bright green. I tried using a UV sterilizer and it worked great but after having it out for a few days, the green water came back. The ammonia is also at a 0.25 which is strange because I've always had 0. Nitrate is about 20-40 and Nitrite is 0.

I'm running out of ideas on what this can be from. The only thing I can think of is maybe I took out too much water and started a mini-cycle? If you have any ideas, please let me know. Thank you!

 

[coralbandit]

Just keep the uv running?
It will cause no harm if you use it 24/7 unless it is a hugely oversized unit....

 

[mambee]

Green water is from too much light and too much nutrients. It is not bad for your fish, just unsightly.

I had the same problem in my 17 gallon tank, and I made the problem go away by adding more live plants. Try adding some floating plants which will grow quickly and consume excess nutrients.

What water conditioner do you use? I know that Prime binds ammonia and gives a false positive reading.

I've found that turning U/V lights on and off shortens the life of the bulb.

 

[ZombieGirl]

I use Prime. It's just strange cause I've never had that happen before. I did get a new light from my brother in-law a few months ago and it may be too strong for my tank. I will try the plants. Thanks for the advice!

 

[Scottishscales]

The green water is algae actually floating in the water that's why the uv works to get rid of it. I've had this problem at least a half-dozen times before. This may be caused by a mini cycle from too big of a water change cause a nutrient spike [nitrate for algae] coupled with the new more intense light.

The suggestion that was given to me was to cover the entire outside of your tank in heavy black trash bags and cover the top so you can still feed them. Keep your lights off and tank covered for about a week. Your fish won't be affected by no light, and as for your pleco losing food it doesnt kill off all of the algae stuck to things but it will starve the algae in the water and kill it without chemicals. The only downfall to this method is it causes a lot of floating debris so you will have to keep an eye on your filters.

To battle the mini cycle I would dose with prime and stability.

"There's always a bigger fish." - Qui-Gon Ginn

 

[woodcatl493]

I had this problem as well. Except my water was brown and looked like crap stew. I did a full water change, cleaned all of the gravel, and the water is crystal clear. I did change my filter at the same time, but I added API Fish Start or something to the tank to prevent a full cycle form happening. I also floated the bio-wheels in the water with the old filter running in order to get all of the bacteria on it. Worked great!
If you don't want to do all of that, I don't have anything for you... maybe in a bit.

 

[mambee]

I wouldn't do a big cleaning and mess with your cycle. Add some floating plants. They will suck up nutrients, shade the tank and provide a treat for your goldfish. I also have a pothos plant growing out of the tank which also uses nutrients.

 

[woodcatl493]

Yeah. That will work better. Get plants like Amazon swords or duckweed to suck up everything in the water. They will grow extremely fast too.

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