various fish with similar body shapes... are these more likely to get along, to fight, or it makes no difference???

[Magnum Man]

I was browsing the fish mongers sites this morning, & saw some Poecilocharax weitzmani, ( black darter tetras ) & I couldn't help but notice they strongly resemble my Crenuchus spilurus, ( Sailfin Tetras ), as far as the shape ( not the color ) actually those Poecilocharax weitzmani, are more colorful, but look to be smaller... it just made me wonder with other unique fish, the question in the title... these could be the Sting Ray shaped Hillstreams, Kuhli Loaches, even Angel Fish... thoughts???

 

[GaryE]

Competition for resources between species always causes trouble in a tank. If the resources they want are similar, then there will be winners and losers.

If you thought Crenuchus and Poecilocharax could co-exist in a tank based on their similarity without researching each species, you'd be wasting lives and money at once. Size would matter a lot there. P weitzmani is a tough fish for most to keep alive.

Family relationships matter when you choose. Generally, shape is a result of environment, and fish are gathered from a lot of places for this hobby. If you have a distinctive looking fish from Peru, and a very similar shape from Colombia, they aren't meeting in nature. Each has a niche they don't share. The same is likely true for your beloved hillstreams. There are a lot of hills and a lot of streams, and similarity usually means competition for resources, especially with the similarity is odd compared to other fish. If they don't meet in nature, they don't usually share habitat in nature.

Midwater shoalers can break that pattern, as flowing water is flowing water and many species can share it. But substrate oriented fish are more specialized.


https://www.researchgate.net/public...ax_based_on_phenotypic_and_genotypic_evidence