Effects of photo period

[seangee]

On fish.
Over the last few weeks I have upped the lighting period gradually from 7 to 9 hours. I initially did this because the plants weren't doing particulary well. It is a blackwater tank so the lighting is quite diffused.

The interesting thing is I have noticed a subtle change in the behaviour of my fish. This is most obvious in the tetras, I have cardinals and glowlights. These seem incredibly relaxed and with the lights on are almost always all visible. They also keep in large groups, although loosely shoaled and not terribly active (except for feeding time of course). I don't mean lethargic - the best way to describe it is they are just lazing around. The sids also seem to spend more time basking out in the open.

The only research I found (admittedly a very quick search) was on the effect on Betta, specifically focused on breeding and growth rates. Their conclusion was that 12-16 hours per day was optimum (for those 2 things).

This has done what I hoped for the plants but I am tempted to keep gradually increasing the period up to at least 12 hours to simulate summer. I realise that I may have to diffuse the lighting further, which won't be a problem for the fish who don't like bright light anyway.

Or am I just imagining it ?

Which also made me wonder if we should also vary the temperature to reflect the seasons in nature. My tanks are pretty much at a constant temp all year. As I live in the UK it is only for a few weeks in the year that the temp rises above where my thermostat is set. I know breeders do this to stimulate spawning - but I have never bothered because I have no interest in breeding.

 

[Colin_T]

Or am I just imagining it ?

You're imagining it and you're going nuts, bwa ha ha haaaa....

Nah just messing with you. I am nuts tho so you probably shouldn't listen to anything I say

Fish do respond to seasonal changes in the wild and this continues in the aquarium if you give them a chance. I use to set my heaters to 18C and that is how cold the water got in winter. In spring the temperature started increasing and by summer the tanks were sitting on 30-32C.

I also had skylights in the roof and windows in the room so in winter the sun came up later and the fish woke up later. In summer the sun came up nice and early and the fish were up early. I did have lights on the tank and they stayed on till late so in winter the fish had about 12 hours of light and in summer they got 16hours of light per day.

Animals and plants on this planet spend about 1/3 of their life resting and 2/3s doing stuff. In winter when days are shorter, birds go to bed earlier but wake up in the middle of the night and spend several hours chatting away before going back to bed for a few more hours sleep. Fish and most animals do a similar thing. Diurnal fishes don't always go to bed when the lights go out and may spend several hours swimming around doing things in semi darkness. In the morning they will often wake up well before the tank lights come on and may breed, fight or do whatever before it gets light.

A lot of fishes actually require a cool period before they can breed. Virtually all coldwater fishes need a cold winter to set things in motion so they can breed in spring. Corydoras breed when there is a drop in temperature, and danias, barbs, tetras and rasboras do best if allowed to chill for a few months each year. They don't have to get cold but their natural habitat can drop to 15-16C when the rains come.

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The optimum conditions for rearing most tropical fish fry is 16hours of light, a temp of 28C, 4-5 feedings per day, and 75% water changes each day, along with good filtration. In these conditions most fish fry can reach 2 inches in 3 months.

 

[AbbeysDad]

When I switched from fish only to a planted tank two years or so ago, I got the 48" Finnex Planted Plus 24/7 LED light for my 60g. I have it on a timer from 6am till midnight running in 24/7 mode. It starts with a dawn light and ramps up to midday sun, then down to sunset/dusk and then moonlight - way kewl and surreal.

I dunno if it's the light, food, or the plants, but my fish are very healthy and breed like crazy. I have sent some 54 molly's to the LFS (for store credit) and am currently growing out dozens of swordtails. I have pulled about a dozen fry from this tank nearly every week!

Fish do respond to the photo period as well as water temperature changes (often increased light and cooler water during water changes promotes breeding, especially in some species). Also, a period of darkness (night) is required for circadian rhythm.

 

[seangee]

Just been playing around with an Arcadia unit I had in my last tank. Its rated at 35W compared to the 44 on the built in one. Only downside is its fully manual. Two channels but only an on/off switch for each. I actually prefer the colour and it has the ripple effect which is cool. Have currently mounted it right at the back so it gets a bit of additional filtration from the spray bar. Also like the effect of having it offset. The straight above light is pretty flat but the one at the back creates interesting shadow effects.

Current plan is to keep using the main light as is and use the dimmer one to extend the period, and I can play with the combination to get a good balance between a nice long day, plant growth and algae.

An unexpected benefit is that I now have a way of raising the rear flap that doesn't involve continually losing wedges behind the tank , Frogbit does well in this tank, but only if I leave a gap to reduce the condensation.

 

[seangee]

Ok so how do I know when I have enough. I don't plan on using CO2 or any fancy fert routine. I'm only doing a weekly dose of flourish complete at the moment and not testing for nutrients (except nitrates).

The growth in the 15G Flex has quite literally exploded. I am up to 12 hours in here. Haven't seen any sign of algae. The planted water sprite and v. spiralis is really taking off. Right now I'm leaving this to go jungle as I do want a nitrate sink and I am trying to use the vals to reduce hardness. It is actually working but so far very slowly, and the pH has also dropped - but again slowly. The duckweed canopy has got quite thick but I am keeping that confined to a relatively small area to avoid having too big an impact on lighting. I do have an area I am trying to carpet with sagittaria subulata. This is healthy and growing (upwards) but olny spreading slowly. I am up to 12 hours in here and my gut feeling is I should continue increasing the period until tha sags start actively spreading or I start seeing algae.

In the 55G the growth in the Echinodorus has accelerated noticeably (I have 3 types). The same is true for the java fern and anubis but these obviously don't grow quickly anyway. The red Nymphea Zenkeri is the one planted thing thing that has really taken off. The floating frogbit is now spreading much faster but I am also constraining these to a relatively small area. The vals and planted water sprite have finally started actively growing and are showing good healthy new growth. Previously they were just surviving. I am starting to see algae. Currently enough to need to clean the glass once or twice a week and I am pulling out a couple of strands of filamentateous alge every few days. There is also some algae starting to form on the leaves of the slow growers. Secretly I'm quite please about this because I have wanted to to add a group of otos for a while but up till now the tank has not been able to provide enough food for them . This tank is up to 13 hours a day. My feeling on this one is I should leave the lights alone now until the plants have grwon enough to surpress the algae and then gradually up them again.

Is my thinking in the right ball park? I have never actively tried to grow plants naturally but really do want to keep it low tech (and low maintenance).

 

[Colin_T]

Give them light until the algae goes nuts. So your bigger tank is probably fine with 13 hours a day. If you add an algae eater then monitor the algae and if it disappears and the tank becomes free of algae, increase the light again to get it back so the algae eaters don't starve.
Make sure you have some driftwood in the tank for any algae eater you get.

The smaller tank can have more light.

If you have Ambulia or Hygrophila polysperma in the tank, they close their leaves up when they have had enough light. The top leaves close up first and gradually the leaves moving down the stem, close up as well. I use these plants to monitor lighting. Once they close their top leaves I wait an hour then turn the lights down or off.
I wait an hour after they start closing their leaves so the plants near the bottom can get sufficient light.

 

[seangee]

Make sure you have some driftwood in the tank for any algae eater you get.

I have 8Kgs (dry weight) of driftwood for my solitary bristenose - do you think I need to get more

 

[Colin_T]

mmm maybe

no I think your probably ok with 8kg of wood in there

 

[AbbeysDad]

Mimicking nature, lighting intensity and photo period can be a challenge, as can water temperature. Depending on the intensity, 12 hours for the aquarium seems a bit excessive, but then we don't really know the performance of the light...not to mention floating plants and/or other light filters. On for extended periods, bright lights can foster accelerated plant growth, but also often require more nutrients and CO2...and then there is the potential for algae (just another 'plant'). The real answer is whatever works. For me, I see no need to push plants for excessive growth as it only means increased ferts and more effort trimming! But 'listen' to the plants as to their light and nutrient needs.
As for water temperature there can be a wide variation in nature. Even in the tropics, rain can bring a cooling effect especially in slower moving and shallow tributaries. I have often heard it reported that like a spring rain, adding cooler water during the water change can induce spawning in some species. Then again, the addition of 'fresh' water always seems to make my fish more frisky. With the exception of my outside tank project, I always maintain the typical 76-78F temps in all my tanks...except water may be a tad cooler during water changes.