irregular / shorter hours of light bad for the fish???

[Magnum Man24 138]

So, I’ve already mentioned Mrs. illness, on bad fish keeping days, I may not get the main lights turned on, on those days… I have sun rise , and sun set lights, that are on timers around my schedule, but those lights don’t typically over lap, and I manually turn on a bright main viewing light, in the mornings, when I get up, and turn that main light off at my normal bed time, after which the sun set lights are already on… if I get too busy, too early, I have forgotten to turn the main lights on, every once in a while, with most tanks in the basement, that results in 6-8 hours of medium light, followed by 4-5 hours of darkness, then 5-6 hours of medium light, again for sun set… just wondering about 2 shorter photo periods with in one day, and how that may effect the fish???

 

[BlaiseinLondon]

Interesting question. I've just been looking at the length of time I can leave the tank lights off without risking the plants, so I'm following with interest..... (Most views seem to be 5-7 days.). I must admit that I hadn't thought abut it bothering the fish - just desperate to keep the heat down.

 

[GaryE23 138]

I think it's going to depend on the origins of the fish. If it comes from a region with seasons, it will have an effect. If it's from right around the equator where the days are the same length year round, then maybe not. Except even there, there are periods when the fish move in and out of light depending on rains and flooding in dark forests.

I've always tried to keep my lights on timers, but I'm a fish breeder, and I know light timing can be used as a trigger for some species (rainbows and Congo tetras come to mind). Yesterday was the solstice (Happy Solstice to those who celebrate it) and that's my cut off for wild plant collecting. Starting now, aquatic plants from my habitat will soon flip a switch and die off in autumn no matter what I try. I have way more success with plants collected before June 21.

We get depressed and people buy fancy lamps in the short days of winter, so we're light affected to varying degrees. It's a fair assumption fish would be too, But when I've killed the lights during the day to get through heat waves, I've noticed no long term effects. I think if it happens over a short period, it hits like a spell of bad weather. That may be wishful, but even if we can pull up papers on one species from one region, it won;t necessarily apply to all. A surface shoaler that hides in sunlight reflected on the water is going to be different from a deep water cave dweller in the same river.

It's unavoidable when a family member is ill, and worth the risk when the heat is bad. I have had fish survive heat waves but show very short lives afterwards - so what we do to try to reduce the damage makes sense to me. I know fishkeepers who use very little lighting, and the fish they choose carefully are fine.

I think it's one of those "do animals get big" questions. Some do...