# stupid question - lighting and fish stress?



## BBradbury (Nov 8, 2010)

*Tank Lighting*

Hello nick...

Aquarium fish are indifferent to lighting. The lack of a time of light and dusk, however, will cause a reproduction problem. How bright or how dark the light is isn't important to them.

B


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## mattinmd (Aug 16, 2014)

I've only seen fish stressed by light when it first comes on, some fish get a bit spooked by the sudden change. 

That said, this isn't entirely absent in nature... the sun goes behind the clouds and pops back out all the time.

As for peak intensity? Please... Even the brightest aquarium lights are positively dim in comparison to full sunlight. How high are you going? 50 PAR? 100 PAR? 200 PAR? 

This article is more saltwater oriented, but look at the time-of-day graphs in the middle.. 10 feet under water in July at noon on a clear day and you're looking at 1300 PAR.

http://www.advancedaquarist.com/2013/12/lighting

That's still 6.5 times more light intensity than 200 PAR provides, and 200 PAR is a heck-of-a-lot in terms of planted tanks.


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## whitepapagold (Aug 19, 2010)

BBradbury said:


> Aquarium fish are indifferent to lighting... How bright or how dark the light is isn't important to them.


Thats not true at all honestly- a complete generalization... Fish absolutely care about how bright a tank is and many will stress if the tank is too bright- especially if there aren't any hiding places.

Some fish prefer a dimly lit tank. Just make sure the fish you keep don't want that.

As long as there is a place to hide, the fish will show you if the tank is too bright- they will all be hiding in the shadows LOL.

Some fish won't act normally and may hide. Some fish may actually stress out and lose color. Some may not eat well if the food doesn't float into the shadows.

In general, light (at a reasonable level), won't harm the fish. BUT you need to know what a reasonable level is. And MANY fish act differently in a VERY bright tank vs a dimly lit one. 

Its something worth considering for sure. As far as little fish headaches? Who knows LOL! The worst thing it does (when its a problem) is stress the fish out which CAN lead to many other problems...


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## klibs (May 1, 2014)

BBradbury said:


> Hello nick...
> 
> Aquarium fish are indifferent to lighting. The lack of a time of light and dusk, however, will cause a reproduction problem. How bright or how dark the light is isn't important to them.
> 
> B


This is not entirely true as particular species like darkness and need places to avoid brightness (elephantnose, black ghost knife, etc)


I totally agree with matt's post and whitepapagold's post. I personally don't really think that your light will ever be bright enough to harm fish's vision or anything like that BUT at the same time some species do not like bright conditions (and thus are usually not well suited for planted tanks)


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## jeffkrol (Jun 5, 2013)

mattinmd said:


> I've only seen fish stressed by light when it first comes on, some fish get a bit spooked by the sudden change.


Yea guppies are quite jumpy.. as are most really


mattinmd said:


> That said, this isn't entirely absent in nature... the sun goes behind the clouds and pops back out all the time.


doesn't "pop" like going from pitch black to on though.. most transitions are gradual at least in terms of seconds or so.. not milliseconds.


mattinmd said:


> As for peak intensity? Please... Even the brightest aquarium lights are positively dim in comparison to full sunlight. How high are you going? 50 PAR? 100 PAR? 200 PAR?
> 
> This article is more saltwater oriented, but look at the time-of-day graphs in the middle.. 10 feet under water in July at noon on a clear day and you're looking at 1300 PAR.
> 
> ...


Err.. most of these fish are stream or lake fish and can easily find shade.


My angels and corys seem to be a "tad" light adverse, though w/ the angels it seems some of this due to acclimation going from weak store lighting to better lighting..

I certainly "prefer" a gradual on/off cycle.
I certainly prefer enough plants so that "if" they so desire they can have some respite..

Is it "crucial"? Probably not.. but is is more natural..

As to high PAR some lights do do "full sun" approx. at a few inches from the surface..at least you can get them or build them that way..

Again these fish are not open ocean varieties either..


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## Catfishguy (Jan 6, 2014)

evil nick said:


> I was thinking of upgrading or once my big tank is set up going pretty high if possible but then it occurred to me. staring at the sun hurts!
> My fish now seem pretty fine but for all I know they may slowly be going blind and dealing with daily migraines.
> Is there any info on how well the fish deal with the stress of high light on them for HOURS in the day?


I'm a firm believer that majority of fish prefer dim lighting,that's why I swear by floating plants to make my fish feel "safe". It's like having a roof over their heads.


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## WaterLife (Jul 1, 2015)

Fish are affected by lighting. All fish vary as to what amount of lighting they prefer. For instance, nocturnal fish that come out at night, but sleep/hide during the daylight. And some fish are from heavily shaded waters from jungle canopies, some places are not shaded, some have high lighting (no overhead shade), but have plenty of plants to get shade from.

In general most fish will be okay in a high light tank. But you can still provide it with floating plants, tall plants or other places to hide if they prefer shaded or dark areas. Some are fine perfectly fine with high lighting. As far as I know, no fish has or will go blind from high light (there is drop eye in Arowanas, but I kept Aros in high light with no drop eye, so lighting doesn't seem to be the reason for drop eye, they don't go blind, just eyes angle downward).

Haven't read any documents stating fish get any eye damage (poor sight, less efficient hunting, swimming into objects, etc) from high light. Lighting and UV rays can damage human eyes, but I don't know if fish eyes can get hurt like that.

So no going blind as far as I know, but stress is a real possibility.
When tank lights come on the fish can go into a mad dash panic. Not sure exactly if it's just a natural instinct/reaction (maybe they think they are more vulnerable/visible all the sudden without the cover of darkness and need to get to safety) or the sudden light just scares them, because maybe they can't see until their eyes adjust.
It is recommended to have lights turn on when the ambient lighting is a bit brighter, so the light differences aren't as significant. The brighter the light, the more stressed fish can get when they turn on. When my low light tanks turn on the fish aren't nearly as freaked out as my high tech tank. Stress is there, as you can tell by some fish breathing more heavily and maybe some color fade (granted some fish need the light to develop color, such as neon tetras) and overall panic swimming craze.

So fish won't go blind, but to reduce stress, more gradually increase light levels (rather than darkness to instant brightness. You can turn on room light a few mins before tank lights, or wait for natural sunrise to brighten room before turning on tank light) AND gradually decreasing light levels at night are appreciated by the fish too (although not nearly as stressed when bright lighting goes to instant darkness or moonlight).


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## Steve001 (Feb 26, 2011)

BBradbury said:


> Hello nick...
> 
> Aquarium fish are indifferent to lighting. How bright or how dark the light is isn't important to them.
> 
> B


How well can you back up this opinion?


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## Argus (May 22, 2013)

*Fish Health:

_"Many recent studies have shown the importance of full spectrum lighting (which will generally encompass a high PAR value) as it relates to health in humans & animals, can be extrapolated to fish as well for a disease prevention which is why good lighting should not be restricted to Reef Marine or Planted Freshwater Aquariums, but to fish only salt or freshwater tanks as well.

In fact the medical community is now utilizing 6400K SHO lights (full spectrum lights) due to increasing studies that show better immune function, mental health, and more. Animal studies support similar results as well."_

Aquarium Lighting Information Guide | Reef Planted | PAR PUR/PAS


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## AbbyV33 (Aug 14, 2020)

I know this post is old but I’m running into a similar issue with some of my fish (5 rummies, 3 Corys, 3 khulis) except for one my betta (sushi). I have a planted tank but definitely want to work toward making my fishies more comfortable. I have notice when I turn on the blue light they seem more comfortable than the regular LED I use during the day. Are there any light suggestions to use for bringing more comfort to my fish while not compromising lighting for plants?


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## Asteroid (Jul 26, 2018)

I really like lights you can ramp up, I think if the lighting gets brighter gradually (as it does in nature) the fish have an easier time and you really only need "bright" light for a few hours. With that being said, providing fish with plants and/or hardscape to escape the light is always a good idea.


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## butchblack (Oct 25, 2019)

Asteroid said:


> I really like lights you can ramp up, I think if the lighting gets brighter gradually (as it does in nature) the fish have an easier time and you really only need "bright" light for a few hours. With that being said, providing fish with plants and/or hardscape to escape the light is always a good idea.


That's what I did. All of my tanks, except the 75g, are on ramping timers. The only reason the 75g is not is that I bought a Vivagrow 24/7 and could not program the custom 24/7 to work. I found a light that I really like the light color on, a Beamsworks DA FSPEC, that also can use a ramping timer with. I will upgrade my 75g to those lights hopefully by the end of the year. A funny aspect of it is that while I prefer the light quality of that over my other lights, my other lights photograph better and I have to correct the color balance of the Beamsworks in Photoshop. It's a minor tweak, so no big deal, but underscores the difference between what we see and what the camera sees.


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## Asteroid (Jul 26, 2018)

butchblack said:


> That's what I did. All of my tanks, except the 75g, are on ramping timers. The only reason the 75g is not is that I bought a Vivagrow 24/7 and could not program the custom 24/7 to work. I found a light that I really like the light color on, a Beamsworks DA FSPEC, that also can use a ramping timer with. I will upgrade my 75g to those lights hopefully by the end of the year. A funny aspect of it is that while I prefer the light quality of that over my other lights, my other lights photograph better and I have to correct the color balance of the Beamsworks in Photoshop. It's a minor tweak, so no big deal, but underscores the difference between what we see and what the camera sees.


Yeah, I don't think I could ever go back to a standard (8 hr) lighting schedule. I like seeing my tank first thing in the morning and late into the night (18 hrs.) Yep, sometimes I have to adjust temp for pics in lightroom. The color with the eye, looks completely different than the camera records it.


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