Hi David, you're quite right in saying that vegetarian plecos are not completely vegetarian. However if the literature is to be believed then phantoms and gold nuggets are specialised Aufwuchs (algal biofilm) feeders in the wild, i.e. omnivores at the vegetarian end of the spectrum. I personally have no issue with you keeping those plecos together and you are feeding them a great balanced diet. However you could have problems if the protein levels are to high in what you're feeding (which i think you've mentioned already). I lost my large royal pleco a while ago and I suspect it was due to the wrong diet. Although I put plenty of green matter and algal wafers in the tank the royal showed a preference for Hikari carnivore tablets which I put in for the goldies and leopard cactus plecos. It would spit out the algal wafers and only eat the carnivore tabs. Its very hard to stop that from happening when they are in the same tank together. It died a few months later with a very bloated stomach. I have also seen a very skinny goldie pleco being kept with healthy royals which were fed largely a vegetarian diet. So its a balancing act if you want to keep largely vegetarian omnivores with largely carnviorous omnivores.