Why saltwater reef fish are more colorful than freshwater fish

[IlhamSetiawan]

I know that there are many species of tropical fish

But, why saltwater fish such as Butterflyfish, Angelfish, Tangs, and Damselfish, etc. Are more colorful than freshwater fish which has more duller color like Tetras, Danio, Barbs, etc?

[Andrew Puhr]

I am not sure how accurate this is but I think they both have adapted colors to blend in more with their environment. Freshwater from rivers and lakes blend in with those earth tones and then you have saltwater fish blending in with the colorful corals in reef environments. I think both are to help conceal them more from predators but I don't know of more scientific reasons. 

[IlhamSetiawan]

On 11/22/2023 at 9:32 PM, Andrew Puhr said:

I am not sure how accurate this is but I think they both have adapted colors to blend in more with their environment. Freshwater from rivers and lakes blend in with those earth tones and then you have saltwater fish blending in with the colorful corals in reef environments. I think both are to help conceal them more from predators but I don't know of more scientific reasons. 

I thinking the same thing but thanks for the answer

[TheDukeAnumber1]

Like Andrew said I think it's all environment too. Freshwater fish have the capacity to have awesome colors, and some US natives do even in the wild, I.E. sunfish can have amazing elcectric blue colors, orangethroat darters can have nice orange and blue markings, southern redbelly dace have beautiful gold stripes and vibrant red bellies especially in breeding colors. IMO it's all about the selective pressures in the environment. If sunfish survival was made better by being solidly electric blue they would be. (breeding project anyone!)

All that said there are plenty of drab colored saltwater fish too.

Sunfish

Southern Redbelly Dace

Orangethroat Darters

Edited November 22, 2023 by TheDukeAnumber1

[Guest]

@IlhamSetiawan, I wouldn't know how to answer, maybe because it helps them blend in with their surroundings? Usually, those types of fish live near reefs with lots of coral or are brightly coloured to warn predators such as sharks (or really anything, it's a fish-eat-fish world in the ocean) of being venomous, I could be dead wrong but that's my take on it. @Andrew Puhr, said the same thing but I also think freshwater fish are less dull-colored (with the exception of betta, blood parrots, neon tetra, guppies, celestial pearl danios, etc.) because of their, again, earthy environment, so they use it to blend in, couldn't explain why some are vibrant although. 

[TOtrees]

Biologist/ecologist here...

First, I have to ask is it really true that sw fish are more colorful than fw?

There are tons of sw fish that aren't colorful, they just don't make it into the hobby. Also, most of the sw stunners are from a particular habitat, coral reefs. On the global oceans scale, this habitat type has ridiculous diversity, but they are very rare. So the fish in the trade are not a good representation of the average fish in the ocean. 

And what about all them african cichlids? And central and south am cichlids? There are plenty of fw fish that are bright and colorful, the question should be whether sw fish as a whole have a higher proportion of species that are "pretty" than fw. I wouldn't hazard a guess on that. 

Then there is the environment question. Fw is generally more turbid and silty, while sw is clearer. Fw fish would need to be brighter to achieve the same effect or result. Those colors come at a cost (cost to produce the molecules/pigments, and greater likelihood of being seen/eaten). Why spend that cost or take that risk (in fw) if you aren't likely to be seen anyways? 

And diet. We've all seen how krill foods make fishies sparkle. Guess what the ocean food chain is based on? Maybe not krill per se, but similar creatures and food chains. All that massive uninterrupted surface area of clear water with rich nutrients gets massive amounts of sunlight, and that powers algae, which powers krill/zooplankton, which feeds the fishies. 

And temperature. Could it simply be that warmer water (whether fresh or salt) is more likely to harbor brighter colors? Could that be related to metabolic rates? Do you think there is more warm fresh or salt water out there in the world, with fish in it? I know where my money is on that. 

Edited November 22, 2023 by TOtrees

[Guest]

@TOtrees, very interesting take, my two cents here although, I think there is a bigger amount of species in freshwater than in saltwater that are dull colored, such as most lake fish (Bluegill, Catfish, and Bass). While other fish such as Gourami, Chiclid, Betta, Guppy, Rasbora, etc. are very colourful and are kept in the hobby. Please contradict me if I'm wrong but take it to DM's as I don't want to take away from this person's question.

[Tanked]

I know a lot of people who go pale and gray when they get cold.

On the rare occasion that aquariums comes up in conversation, SW/FW color is is the most common reason given for going SW.  Diet, location, temperature, and size could all be contributing factors. If my LFS is any measurement, most of the SW fish I've seen are larger, so they appear more colorful.  I think that there are more choices for FW color. 

 

[nabokovfan87]

it's about camouflage.

Background for a lot of "saltwater fish" is actually more aptly called reef fish and the background is bright and colorful.  The fish are then colorful for that reason.

The background for freshwater fish is a bit more drab and a bit more barren of color.  Some do have a TON of color and that is used for things from mating to all sorts of other reasons.  Frogs and reptiles use color as a warning. 

I would take a nice looking white cloud over a lot of saltwater fish out there.  HECK. My RTBS is a beautiful fish.  Everyone has different things they define as beautiful.