How Important is Accurately Recreating Environmental Lighting

I've had two community tanks with tetras, gouramis and catfish for almost a year now, and there really isn't any indication that there's a problem, but try as I might I can't help but feel like I'm doing something wrong when it comes to lighting. So just for my peace of mind, here's a timeline of daily lighting for my tanks.

Sunrise -> 6:00 Tank Lights & Room Lights On -> 9:00 Sunset -> 8:30 Tank Lights & Bright Room Lights off -> 9:00 All lights off -> 11:00

Total Time in Darkness (Only Moonlight) - 7 hrs

Total Time with Dim Sunlight/Artificial Light - 5 hrs

Total Time in Full Light - 12 hrs

I'd appreciate any advice, and if you know of any articles or studies done on this or related subjects, that would also be really cool because it's interesting to me that I hear so little about this. I know that fish and plants have different tolerances or needs when it comes to lighting, but just how important is it really? What effects could occur from providing habitat-inaccurate lighting to fish, whether that be too bright, too dim, too short or too long?

Lighting is extremely important to fish, and for that matter to all animals including humans. We all have a circadian rhythm biologically, and every cell on our bodies detects light. In fish, this is very strong.

Fish must have a period of several hours of total darkness--no tank moonlights, no room light, no daylight entering the room. Blackness. For most of us, this will be during the 10pm to 4 am period, whenever it is dark outside (depending upon the time of year) and no room lighting.

The "daylight" period has to be a continuous period as well, and should not exceed 12 or so hours. Usually, this period is geared to what the plants need (if live plants are present) as excess can cause algae issues. My tank lighting is on for 7 hours and no more. There is daylight (filtered through closed blinds though) before and after this period, then the total night blackness.

The intervening hours, between the darkness and daylight at either end, is less important, but it is best to have the tank lights off after the "daylight" period ends; a brief "moonlight" is OK.

One of our members has a blog site, and some of my articles are posted there, including one on lighting, so please have a read, it will answer your questions.

Byron said:

One of our members has a blog site, and some of my articles are posted there, including one on lighting, so please have a read, it will answer your questions.

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Thank you very much, that was exactly what I was looking for, and a fascinating read. Based on your comments and what I read, it sounds like my current schedule should be OK, but I'll try to reduce the photo period and brightness a bit during the tank light hours, as I'm pushing it with 12 hours of direct light.

My only question is, do you think I should keep the blinds down like you do? It might extend the time of darkness a bit in the morning; my tanks are on the western side of the house, so they get less morning light anyway. However, it may then become a problem to get the room light on at a regular time. Also, can you share what your lighting schedule is for your tanks?

As Byron points out, like us, fish are best served with a normal circadian rhythm, which requires a period of total darkness.
Having 'said' that, tank lighting is more for plants and our viewing pleasure than for the fish...as fish navigate just fine in very dim or murky waters.
I have a finnex planted plus 24/7 light on my 60g display tank in 24/7 mode that I have on a timer. It comes on at 7am in a yellow sunrise and slowly ramps up to bright light noon till 3pm, then ramps down to a sunset and off at midnight. This makes for a pretty surreal environment. However, I have many other tanks where lights just come on at 7-8am and off at 7-8pm (although they have a lot of floating plants that lessen the light penetration.

Gemtrox42 said:

Thank you very much, that was exactly what I was looking for, and a fascinating read. Based on your comments and what I read, it sounds like my current schedule should be OK, but I'll try to reduce the photo period and brightness a bit during the tank light hours, as I'm pushing it with 12 hours of direct light.

My only question is, do you think I should keep the blinds down like you do? It might extend the time of darkness a bit in the morning; my tanks are on the western side of the house, so they get less morning light anyway. However, it may then become a problem to get the room light on at a regular time. Also, can you share what your lighting schedule is for your tanks?

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My lighting schedule was worked out to deal with black brush algae. I have moderate, some would say low, lighting to begin with, but my fish come first and plants have to be those that can manage. And all tanks have a cover of substantial floating plants, and I know these make a difference to fish. I worked the tank lighting down to seven hours a day, and at this level the problem algae no longer increased (it had been for a couple years, and I had been experimenting with lighting and fertilization). I then noticed that the brush algae did increase in the summer, and I figured out that this was due to the additional length and intensity of daylight in summer compared to winter. My tanks were then in a dedicated fish room, so it was no issue to thickly block the light; I had blinds and drapes, and even used tin foil on one set of windows. It worked; for the next 3-4 years, no increase in problem algae.

My 7 hours are during the day, but being retired I am home most days so here to enjoy and work on the tanks. The tanks are all on a timer, and come on at 10 am and go off at 5 pm; in winter with the time change it becomes 9 am on and 4 pm off. But throughout the year, this means the tank lighting comes on and goes off when there is ambient daylight in the room. I'm in a different house now, and the window has a blind that is always closed but sufficient ambient light gets through. Years ago when I was working and only home evenings, the schedule was different and I had a room light on another timer so it came on just before the tank lights went off, thus avoiding the light shock for the fish.

Byron said:

tank lighting is on for 7 hours and no more

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Only 7 hours of full lighting ? How many hours of full blackness ?
Could you please give the type of lighting you use and the provided lumens ? And plant species your tanks house ?

Could what you call intervening hours be considered sunrise and sunset ?

Avel1896 said:

Only 7 hours of full lighting ? How many hours of full blackness ?

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Darkness depends upon the time of year, so during summer the darkness (no light in the room of any sort) is from 10 pm until 4 am or thereabouts. As the days become shorter now, and we approach the winter, the darkness will then be from 5 pm to 7 am or thereabouts. Having a dedicated fish room, I can let this play out naturally, just ensuring that the tank lights are on for 7 hours during the "daylight" period.

Avel1896 said:

Could what you call intervening hours be considered sunrise and sunset ?

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Yes, but I do not provide any artificial lighting (moonlights, etc) for this, it is just the natural dawn and dusk occurring outside. The window blinds are sufficient to prevent direct sunlight, but not daylight entering, so I can make use of this rather than having to run additional room light. This is again a benefit of having the fish tanks in their own room, so windows, lights, etc can be controlled solely for the benefit of the fish.

Avel1896 said:

Could you please give the type of lighting you use and the provided lumens ? And plant species your tanks house ?

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I am still using T8 fluorescent because I have been using this since the 1980's (it was T12 then), and I understand it, and I have tried a number of different tubes for intensity and spectrum. I've no idea what the lumens are, because I know that one tube or two tubes over a tank will allow me to grow "x" plants. I use 6500K spectrum tubes on all single tube tanks, and on dual tube tanks one 5500K and one 6500K. And I use good quality tubes, the Life-Glo for 6500K and the ZooMed Tropic Sun for the 5500K. The GE, Phillips, Sylvania tubes in the small sizes are no where near sufficient intensity as the same wattage Life-Go and Tropic Sun, but these did work well over my 4-foot dual-tube tanks when I had them.

Echinodorus (sword) plants do well in my tanks, as did crypts. All tanks have floating plants, Water Sprite mainly, some Water Lettuce, and Salvinia. My Frogbit struggled for years (found out it was a temperate not a tropical species of Frogbit) and I finally got rid of it. Pennywort did very well for a time, then suddenly struggled. They've been messing with our water unfortunately, and I have noticed the plants have not been as good as before this started. Here are some photos of what a few of the tanks were like in the good old days when I had zero GH/KH and pH 5 water out of the tap..

Byron said:

it is just the natural dawn and dusk occurring outside.

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Are you aware how damn lucky you are to not need any artificial bulb except for full hours lighting (kidding here )?

So if I may sum up :

- you follow (light) seasons cycle.
- you don't need artificial bulb to mimic sunrise and sunset
- your Echinodorus, Cryptocorynes, floating plants, flourish(ed) with zero GH/KH and pH 5 water and only 7 hours full lighting
- you "had zero GH/KH and pH 5 water out of the tap" seems miraculous to me ! How it is now ?

What do you fert if you fert ?

Avel1896 said:

- you follow (light) seasons cycle.
- you don't need artificial bulb to mimic sunrise and sunset

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Correct. My 7-hour "daylight" period when the tank lights are on can be any time during the day now, so it is easier to have this scheduled to take advantage of the natural seasons. The other benefit is that the tank lights are on for the same period and at the identical time each 24 hours. I don't need to adjust the timer at daylight savings or standard time changes, and that more closely replicates the tropics where the day and night are pretty much the same all year.

Avel1896 said:

- your Echinodorus, Cryptocorynes, floating plants, flourish(ed) with zero GH/KH and pH 5 water and only 7 hours full lighting

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I did/do use fertilizers. Flourish Tabs for the large swords, this has been constant for more than 10 years since I first tried them. I was using liquid fertilizer, Flourish Comprehensive Supplement for the Planted Aquarium, just one dose a week. I have not been using the liquid since last December, due more to my medical conditions than anything else, and to my surprise it did not make too much of a difference. I have started this up again, as I think the floating plants could use it.

Avel1896 said:

- you "had zero GH/KH and pH 5 water out of the tap" seems miraculous to me ! How it is now ?

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This is problematic now, but before they started messing with the pH the zero GH/KH and acidic pH was ideal for my tanks of very soft water (and then mostly wild-caught) fish. I had aquaria in the 1980's when I lived in Victoria, who had zero GH/KH and pH 5 or lower water. After I moved to Vancouver the water was much the same until they started messing with the pH in the early 2000's. I wasn't aware of this, until one week two days after the water changes all the crypts in all the tanks melted completely. Knowing this was almost certainly due to some change in the water, I tested and found the pH was now 7.0 due to the addition of soda ash. This dissipated out very quickly in the aquarium, but the crypts couldn't tolerate the sudden change from say 4.5 to 7. No other plants, and no fish, seemed affected over the next several years. This past Spring, they upped the pH to 8.5 with more soda ash and something else. I've reduced the volume of my water changes, and am considering options now. We still have zero GH/KH, it is only the pH they are messing with, to prevent corrosion in the pipes they say.

Byron said:

I don't need to adjust the timer at daylight savings or standard time changes, and that more closely replicates the tropics where the day and night are pretty much the same all year.

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I also have a convenient timer which is currently set on 10 hours full lighting as I do not have any dimmer coz my LEDs aren't dimmable. It is 6300°K and provide 830 lumens. Do you think I should decrease hours of full lighting OR change for a dimmable LEDs ?

Byron said:

Flourish Tabs, Flourish Comprehensive Supplement for the Planted Aquarium

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I'm using JBL© Proflora (root)balls, Dennerle© liquid plant elixir alternately with Tropica© specialised nutition.

Wow 8.5 pH and GH/KH = zero ? What do they add in tap water ?

Avel1896 said:

I also have a convenient timer which is currently set on 10 hours full lighting as I do not have any dimmer coz my LEDs aren't dimmable. It is 6300°K and provide 830 lumens. Do you think I should decrease hours of full lighting OR change for a dimmable LEDs ?

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Unless you have algae issues and/or plant problems related, there is no problem with the 10 hours. Having it consistent each 24 hour period is important for fish even more than plants.

The problem for me anyway with dimmable lighting (don't have it, see no need to get it) is that any light is affecting the fish, not necessarily to imply negatively, but light is light and fish expect it to be the same every day. This was clearly evident in the data I cited in that article. If my planted tanks are fine with 7 hours of overhead light, the fish will be too. It is not bright anyway, though when I thin out the floating plants it is noticeable that the fish do not appreciate this increased brightness, and move down in the tank for several days until the "cover" re-grows. The dusk and dawn periods are lengthy, but natural daylight.

Avel1896 said:

Wow 8.5 pH and GH/KH = zero ? What do they add in tap water ?

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From the Water Board's website: To adjust the alkalinity and keep the pH level stable, Metro Vancouver adds lime and carbon dioxide (at the Seymour Capilano Filtration Plant) or sodium carbonate and carbon dioxide (at the Coquitlam Water Treatment Plant). These additives in no way impact the flavour or safety of our drinking water.

Byron said:

Unless you have algae issues and/or plant problems related, there is no problem with the 10 hours. Having it consistent each 24 hour period is important for fish even more than plants.

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It is consistent each 24H and adjustable in 15 min increments.
I have some hair algae from time to time.

Byron said:

fish expect it to be the same every day.

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Maybe I used the wrong word : to me a "dimmer" is device/tool allowing lighting to turn on progressively up to 100% of its power (if desired) and then turn off progressively down to 0% lighting, providing a light cycle which is the same every day. In France we call it a "dimmer".

Byron said:

These additives in no way impact the flavour or safety of our drinking water.

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In France, since the very beginning of covid19 crisis, tapwater suppliers are adding chlorine and chloramine up to make us recoil because of odor......

Byron said:

And all tanks have a cover of substantial floating plants, and I know these make a difference to fish.

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My tanks will soon have honey gourami in them. Right now I have duckweed covering 95% of the surface, and I know gourami need access to the surface to breathe. Do you have any experience or knowledge about what I'd need to do for the gourami in this situation?

Gemtrox42 said:

My tanks will soon have honey gourami in them. Right now I have duckweed covering 95% of the surface, and I know gourami need access to the surface to breathe. Do you have any experience or knowledge about what I'd need to do for the gourami in this situation?

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95% is a little too much. As you pointed it, Trichogaster "honey gourami" chuna need to regularly breathe at the surface like every single labyrinthidae fishes. You can remove some floatings and put them in another tanks.
To avoid an "invasion", you should stretch a clear hose of the smallest diameter between aquarium walls, this would prevent effectively - while remaining discreet - any floatings invasion.

I have duckweed in one tank (deliberately), and regularly I scoop out some and toss it in the compost. It can reproduce incredibly fast. Good floaters for fish are substantial plants like Water Sprite, Frogbit, Water Lettuce, and some of the stem plants grow well floating too.