C. Robertsoni are the only one that I’ve kept, and I found them to be extremely intolerant of their own kind. Perhaps it’s because I was only able to purchase 3 of them (it’s all the LFS had). I put them in a 125g without any other fish —(maybe that wasn’t large enough) and the two larger ones each immediately claimed one side of the tank. Within a couple of hours, the smallest one was dead, and the other two were each in opposing corners of the aquarium with fin and scale damage. Whenever one would catch a glimpse of the other, it would immediately charge out and attack the other. I quickly divided the aquarium off, and ended up trading one of them to a friend of mine. We each had our solo ones for years, with firemouth cichlids and various non-cichlids. They were both extremely peaceful towards all other fish, unless provoked.

 

+1 to @oldcatfish on keeping Cribroheros robertsoni.
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My own experience with a WC, juvenile group placed initially in a 180 gallon tank, was with a species that was peaceful and did great when kept in the aquarium as a mature individual, or sort of good as a somewhat compatible, young pair (the female looked like she had been run over by a lawnmower a couple times, after spawning with the male).
In Honduras, they seemed pretty much okay with each other in high current areas with a lot of big rocks. So, they are definitely a rheophilic species. And in the wild at least, we didn’t see a lot of fin and scale damage caused by scraps with each other (unlike what @dstuer informed us with his experiences in the Cenotes of Mexico with Rocio octofasciatus, who seem to live naturally in a state of almost undeclared WAR with each other…..).

 

In Honduras, they seemed pretty much okay with each other in high current areas with a lot of big rocks. So, they are definitely a rheophilic species. ..).

When ever kept these species successfully, as long asstrong currents were applied aggression was minimal.

As you can see by the bend of the Vallisneria in the rostratus tank, the flow rate gave them something to pit, and vent their excess energy against, as opposed to focusing on each other.
Whenever I´d put any of the genus Cribroheros in a normal flow tank, there was usually aggression, so
beside a heavy flow from the sump, adding a couple wave makers tempered that aggression.

I get the feeling what most aquarists deem as too much flow, is simply only adequate for many even semi-rheophillic species, including most central Americans
riverine species, , and Geophagines.
Compared to the rivers where I collect, even my 1500 gph sump flow and the addition of the 2 wave makes in my 6 ft tank, my normal flow is quite wimpy, compared to the waters they normally exist in.

The flow of the Margaritas below, is where I caught the Darienheros above.
https://youtu.be/ZQ-qgq1XuCQ

 

Great video! And that visual info makes a lot of sense. The water current in those rivers we collected C. Robertsoni from in Honduras, was strong enough in some parts (even though the water was only about mid-thigh deep - near the dry season), that it was difficult to maintain your footing.
That’s powerful current!

 

Part of the problem could have been the current thing. I had 4 Aquaclear 110’s on the tank, but no power heads or wavemakers. But my limited knowledge of C.Robertsoni was that there were 2 variants, one that was from faster currents and one that was not. I had only read this though…I certainly didn’t have any firsthand knowledge. This was back in the early 1990’s and C. Robertsoni was newer in the hobby. The LFS thought that they were related to T. Meeki, and had them for sale as “Turquoise Firemouth.” I recognized what they were immediately, and made an impulse purchase. I had just started a fish room at the time, so had a couple of empty aquariums.