I had a earth eater and a parrot fish they both liked eating there own crap.. I watched closely, like most fish they taste the poo and then spit it out, but these two cleaned the tank I thought it was sick when I first spot them eating there crap, thought it helped me by cleaning the tank lol No other fish I've owned done that. Look at the piranha measure it with a dovii which one is smarter? dovii, dovii's are loners in the wild and are aggressive, dovii's take care of them self's. while piranhas have to be in packs other wise they will get eaten or killed.
Is the first an illustration of fish intelligence from your perspective?

