how much do you think the "right" light effects fish

[Magnum Man]

so, fish are found in nature, from sunny spots, to deep shade, and aren't really exposed to funny un-natural colors, and for example, I had an aquarium LED light that was failing, and started flickering... it was driving me nuts, so I stopped using it... assuming if the flickering light was driving me nuts, it likely had the same effect on the fish... plants like particular spectrums of light, would it be wrong, to assume fish do too??? I think the bulk of the south American tetra's come from shady streams, while it seems my Hillstream's must come from sunny areas, by their diet of biofilms... I have a blue background on one tank that is backlit... I'm wondering if the Cory's don't like that blue light, as they don't seem to be doing as well long term in that tank, as I had hoped... then in my thread about aquarium LED lights not lasting long enough, there were members using screw in, lights... just wondering about best for fish, lights, and spectrums...
and wondering if matching a fish's light preference is as important as matching it's water preference for long term life???

as a weird example, could the use of black lights, as are commonly used around glo fish, for their "cool" effect, actually be shortening their lives, or other non glo species kept in the same tanks???

 

[GaryE]

I can't comment on spectrums, but intensity is really important. I find a lot of fish with very strong markings dislike bright and intense light. That's the domain of silvery fish, who use reflected light as their camouflage.

Some of the streams I've been in both Central America and Central Africa are dark - I'm talking just at the end of sunset dark. You step out of the jungle onto the sunlight scar of a road, and your eyes have to adjust, even at noon.

I have an interesting tank right now. Because of filtration flow, all the floaters are bunched at the end of the four footer, in about half of it. The sand/gravel substrate in the other side has a lot of Cryptocoryne growing in it, but no plants in the upper levels. All the fish (2 Cichlid species, a lampeye and an Aphyosemion) stay on the dark side. One species, Chromidotilapia kingsleyae, will dart into the lighted half at feeding time. It's a species I watched adults of in sunlit waters in a wide, shallow river, but I saw no juveniles there. I'm wondering if the dynamics will change as these are young, 2-3 cm fish now.

 

[Magnum Man]

interesting... the Denison Barbs seem to be thriving in my bright Hillstream tank, and being highly marked, seem to have no issues out in the open, in that brightly lit tank, but do spend about 50% of the time in the shade of the pagodas, either under them in the space created by the legs, or they actually go inside them under the roof, but for the most part, all the fish in that tank spend nearly equal time between the shady spots, and the brightly lit open areas

 

[Colin_T]

I can't comment on spectrums, but intensity is really important. I find a lot of fish with very strong markings dislike bright and intense light. That's the domain of silvery fish, who use reflected light as their camouflage.

A lot of fishes that come from black water (tannin stained) have brighter markings so they can see each other in the dark water. Neon and cardinal tetras are classic examples but a rainbowfish from New Guinea (Melanotaenia rubrostriata) comes from black water and the wild caught fish have intense red lines on their bodies. When they are kept in aquariums with clean water and no UV light, they fade in colur. Pseudomugil mellis is the same and comes from black water in Queensland but loses colour when kept indoors in clear water.

UV light helps improve colour in rainbowfishes but can be detrimental to fish from black water, especially if the black water habitats are shaded. UV light can also cause skin cancer on fish and albino fish are susceptible to this.

Ideally you want to use lights with a 5500-6500K (K is for Kelvin) rating so they have red, blue, green and yellow light, which is close to sunlight. This temperature doesn't have UV light and is safe for aquarium fish.

Lights with a 15,000-20,000K rating have lots of UV light and can be beneficial to corals in marine tanks and to some open water fishes like most of the rainbowfishes, but isn't good for most other types of fish.

 

[Magnum Man]

if you think about the old fluorescent lights for aquariums, lots had a lot of red/ blue spectrum light, and were on all day... the new LED's we can adjust, but I think typical sun rise / sun sets use those colors, but mid day's seem to be mostly white lights... wonder if that is healthier for the fish....

back in the old days, I had a reef tank, and used a High pressure sodium light for sun rise, and sun set, and a metal halide light for most of the day ( red spectrum morning and night, and white spectrum through out the day )

 

[TwoTankAmin]

I think spectrum matters more than temperature. I have always preferred bulbs with high CRI ratings as the fish look more like they do in nature. most of my bulbs are full spectrum.

A color rendering index (CRI) is a quantitative measure of the ability of a light source to reveal the colors of various objects faithfully

I learned early on with lighting that higher CRI full spectrum bulbs made fish colors pop. Even in the days of T-8 fluors I used this sort of bulb even though they cost a lot more.

There used to be a UK made full spectrum high CRI bulb- they were made by a company called Triton. The problem with getting them in the USA was the company would not replace bulbs broken in transit to the USA which caused many of the US companies to stop bringing them in. Today for my older T-8 lighting fixtures I use the Zoo Med Ultra Sun bulbs, They have a CRI of 98 on the scale of 1 - 100. They are also full spectrum including UVA. They are 6500k.

I would think that a bulb that reproduces light like the sun =would be fine for fish in a tank as this is what they get in the wild.