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Let's Talk Green Water!


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I have a 20 long tank that runs a little green. And by little, I mean, there's always a little tint to the water, but never cloudy. The water is always fairly clear and I've not had blooms that I've noticed. Usually, if the tint gets a little greener than I'm happy with, we just do a 25-50% water change, limit the light for a day, and it's all good.  The tank has run this pattern for several months.

A little background on the tank, it's only housed a red-tail botia loach and rams horn snails regularly for several months. There has been the odd crooked-spine guppy now and then until a few weeks ago. I run 2 medium sponge filters in it. I've added 2 squirts of Easy Green the last 3 Mondays. 

2 weekends ago, we added some substrate (aquarium gravel) and crushed coral, and added some driftwood. We also removed some potted plants and added some other planted plants. And we added 13 Green Tiger Barbs (who'd spent over 3 weeks in the medicated QT tank). The light is new. It's a Nicrew ClassicLED Gen 2 and I keep in at 50% white lights only and it's on for 10-11 hours a day.

I've noticed the last couple of days, it's been the slightest bit cloudy. Not like a bloom, but just not crystal clear like usual.

Ammonia - 0

Nitrates - 10

Nitrites - 0

GH - 200

Chlorine - 0

KH - 100

pH - 7.6

Temp 76*

So what makes the water green? And check out the video. That is at 8x magnification on my Galaxys10e Pro Video. That is definitely lots of life teeming in the water. Any idea what that is? 

And you're welcome for the close up of a rams horn snails' egg clutch. At more magnification, you can see each egg in its little pouch...quite amazing!

I appreciate y'all's input! Thank you for reading. 

Alesha (akconklin)

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9 hours ago, akconklin said:

So what makes the water green?

@akconklin I was asking myself that on Wednesday of this week. Below is my baby sparkling gourami tank and I use the green water to feed the babies. My goal is to keep the water green.


When I look at it under the microscope it looks like thin little green footballs. These are the free floating algae called phytoplankton. There are also quite a quite bit of rotifers swimming around and these are green also because they have been eating the phytoplankton.

There are Daphnia in this baby gourami tank that also eat the phytoplankton so unfortunately if I don't add more green water, it begins to clear up. I get the fresh stock of green water from this tank below.


The trick to keeping the water green is extra heavy feeding of the fish and plenty of light. I feed the swordtails several times a day with generous portions of Vibra Bites and blackworms and baby brine shrimp. I also run extra lights on the tank for at least 10 hours a day, sometimes more. And finally this tank does not have a Daphnia population (swordtails eat them all) to consume all the phytoplankton.


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Thank you, @Daniel.  This answer is amazing.  And I've had to mull it over to understand some of it. I did have to look up "rotifers", as I wasn't familiar with the term.

My water never gets as hazy or chunky as yours appears to be, so I'm guessing it's probably not a delicacy for baby fry at this point in time.  My lights are on for a good part of the day and I do feed quite a bit, but it's just the snails, loach and barbs, so really not too many mouths to feed. (The other tank has hundreds of guppies. Feeding that tank is compleeeeetely different than this one!)

So, that's why mine clears up with water changes, I guess, because I'm getting rid of some of the phytoplankton. And it's probably if I'm overfeeding that I notice the green "growing".  I think I understand now. 

I appreciate your time and your thorough explanation. Thank you.

Alesha (akconklin)

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