vegetarian fish

Well to be honest, I've seen nearly all of my fish eat a deceased tankmate on the bottom of the tank before, and all of my fish go crazy when I feed them bloodworms.
 
I can't think of many fish that are strictly herbivorous (as in they eat nothing but veggie matter). Even most plecos are opportunistic and will eat certain meaty foods if they get the chance.

But as far as fish that are largely herbivorous, most headstanders (Leporinus, Anostomus, Abramites, etc.), siamese algae eaters, silver dollars, goldfish, mollies, plecos, mbunas. And many others that I can't think of offhand.
 
Most fish will eat about anything you give them (and be happy about it) but certain fish simply can't have meaty products. My saulosi or tropheus would be delighted to eat a bunch of bloodworms, but I'd have bloated, soon to be dead fish... It's very important to know if you have a strict herbivore. Other fish, such as most plecos, eat a lot of greens but have flexibility in their diet.
 
All fish are opportunistic eaters. Just because one species is normally an herbivore, doesn't mean they'll pass up food because it's a chunk of meat. Fish grab what they can, whenever they can get it. It's survival 101.
 
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