# Window light - OK or not OK?



## boomstik (Feb 4, 2015)

Hi forum,
This is a repost from GTAAquaria.com - hoping it will get more traction here.

I'm getting lots of conflicting advice from research around the 'net, as well as from my LFS, with regards to putting a tank near a north-facing window.

The tank is a standard 10G, and sits 90º to the window, with is short side near a wall. So the only light it's getting from the window is on its front and top (there's no cover). I'll try to illustrate (view from top):


```
East
        ├┈┈┈┈┈┈┈┈┈┈┈┈┈┤ ⬅︎ east-facing window
      ╦ 
      ║  ┌╍╍╍╍╍╍╍╍╍┐    ⬅︎ black background blocks light
      ║  │                 │
wall  ║  │      TANK       │
      ║  │                 │
      ║  └─────────────────┘
      ╩         Front
      ┬         
      ┊      ↗↗↗↗   
      ┊     ↗↗↗↗  window light
North ┊    ↗↗↗↗
      ┊
      ┴
```
To expand on these conditions:

- The front and top of the aquarium are getting most light.
- The east-facing window is always in the shade, never gets direct sunlight.
- For the purposes of this exercise, let's assume there is no artificial lighting (in fact there's a little room lighting at night, which we can consider negligible). 
- The front of the tank will get a little *direct* sunlight at dusk in the summer, maybe an hour just before sunset. At all other times, it only gets diffused light.
- There's a 13 watt or so CFL (the cheap kind) i've been turning on every night for about an hour after dark, just while i'm getting this figured out. I'd like to get rid of it, as it's 1) ugly and 2) cheap = low CRI and I assume so is PAR/PUR. Let's ignore it for now, although it may have contributed to my plants' growth so far. (I've only had it for a week, so maybe not).

So what I'm trying to figure out is, being located in downtown Toronto, would these be considered low or medium lighting conditions? I don't imagine this would count as "high". I know window lighting is unpredictable, but the advice I've heard so far has ranged from "No way, this is the worst possible lighting, your plants won't grow" to "This is too much light, you'll get lots of algae". Is there no consensus? Am I a unique snowflake, and does no one else have a planted tank under these conditions?

So far I've got some anubias, java fern, and rotala rotundifolia. They seem happy, I'm seeing a bit of growth on all of them over the last month, and the java fern is making babies. I had a bit of brown algae as the tank was getting established, it's gone now. There's a small canister filter, and the tank is about 60% stocked according to AqAdvisor (neons, cardinals, and a chainlink loach). There's no CO2 injection, though I'm thinking of adding a DIY setup maybe if it's appropriate. My ammonia/nitrite/nitrate levels are all healthy. Water changes 30% weekly. I do not dose any ferts.

I'd really like to add some carpeting moss, but was told that I should forget about it unless I get artificial lighting.

Any thoughts on this from the community?

Thank you!!


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## klibs (May 1, 2014)

It can be done. There are some users on here that use light from windows to grow tanks. Most shy away from it because the variable amounts of light can lead to algae breakouts.


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## DevilDogDoc (Dec 12, 2014)

My 60 was by a window for a while and it was an algae farm.


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## micheljq (Oct 24, 2012)

My tank was in a quite lit place in the house in the summer. If you tank is getting direct sunlight, you can consider you have high light. I saw my Bacopa Caroliniana grow like mad under the sunlight, and pretty in all of its glory. As my Bolbitis heudelotti who began growing like crazy as well, and very pretty. Limnophila sessiflora too, in pretty bushes, it did stop growing just in lenght.

Problem is that the light is not consistent, from one day to the other, over the summer and winter, quite different. In the summer especially the lighting period is long, and intense (and i am in the north, Quebec). I had green water problems beginning on the last week of may and june and july. Tank was moved somewhere else in july, because my wife did want it near the TV room. I would have like to continue my personal experimentation with sunlight.

I think you would need something to block/partially or completely the windows on certains periods of the year, when light is intense and day quite long.

Some experienced people are able to maintain a tank under these circumstances, most don't.

Michel.


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## Steve001 (Feb 26, 2011)

boomstik said:


> Hi forum,
> This is a repost from GTAAquaria.com - hoping it will get more traction here.
> 
> I'm getting lots of conflicting advice from research around the 'net, as well as from my LFS, with regards to putting a tank near a north-facing window.
> ...


You have got north light equals low to _maybe_ moderately low light. The fact that your plants are growing without adding ferts. and co2 suggests this is correct. Could you post a photo of this tank?

I've been running my tank on natural light for about 15 years I think. It sets near an east southeast facing window. Starting in late August-early May it gets direct sunlight for a few hours. The only algae is what grows on the glass. I would not worry one bit about fluctuating light levels. During the Winter months I will supplement with this light sometimes http://www.eiko.com/Products.aspx?CatID=94


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## boomstik (Feb 4, 2015)

Thank you all for the replies. Your responses both confirmed and disproved some of my theories about this . I'll get a couple of photos of the tank as soon as I figure out how to do so without everything reflecting in the glass (since there's no artificial light to overpower the natural light causing the reflections).
Since the last post, I made several observations:
1) the anubias started developing yellow/brown tips, only on the leaves closest to the cheapo CFL I had running for a couple of hours at night.
2) simultaneously, I noticed brown algae on the glass, also only in the area near the CFL.
-- Result: bye bye CFL - clearly you produced too much light. Without the CFL, for the last week, no more brown algae and the tips damage on the anubias seems to have either slowed or stopped.
3) in addition to making small baby plants at the ends of the old leaves, the Java Ferns are growing new young leaves. There are at least 4 of them on 3 separate rhizomes.
4) Today noticed one of the Anubias has sprung a new leaf. It's actually the plant that's farthest away from any light, and is mostly in the shade most of the time.
Water parameters are always testing near perfect, and the tetras and the loach are all happy and colourful.

All of the above leads me to believe the light levels are actually pretty close to perfect right now, at least for the plants and livestock I currently have. I will start changing things up a bit from here, and hopefully not mess up the good thing  Let's see what happens as the days get longer and the tank receives more light. Considering this is my first tank, I'm either extremely lucky, or extremely nerdy, or both 

Thanks, all, I'll post pics and updates.

Bump: @Steve001, thanks for pointing me towards those bulbs, I actually ordered a couple of very similar ones a few days ago, just in case. 90+ CRI, 5500K. Those are actually excellent bulbs to use around the house, as the colour rendering is outstanding. My wife is an artist, and she immediately expropriated one for her worklight.

Another interesting observation: under those lights, you can actually see the difference in the Nitrate colour chart from the API freshwater master test kit. Contrary to the popular belief, the swatches are NOT the same shade of orange! Go figure.


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## fish jihad (Mar 1, 2014)

As others have stated, natural light is too variable. However you sound like a man willing to experiment and be patient. When you add light to a low light plant and get algae its due to low ferts most likely. So if you add a CFL then consider getting some seachem flourish or other comprehensive liquid fertilizer. You will likely only need a fraction of reccomended dosage since your leaning on window light for now
Id suggest googling ferts for low light plants and see what comes up.

Window light will grow plants. But time and experience has taught others that its too unpredictable. So most eliminate that variable and get artifical light


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## Hillmon (Aug 3, 2014)

Dustinfishtanks - a youtuber that I am subscribed to has a ton of tanks in a green house and seems to do fine, idk why this couldn't work. I would test it out and adjust co2 and other factors as conditions develop or issues arise.


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