Here's why this question is difficult to answer:
* "Pacostimus" is not a recognized fish species. There's no known fish with that name.
* "Allege" is likely a misspelling of "algae." Algae are plant-like organisms that can be found in tanks, but they are not a suitable food source for fish.
To help me understand your question, please clarify:
* What is the actual name of the fish you're asking about? Can you provide a picture or more details about its appearance?
* Are you asking if the fish can survive on algae alone? If so, the answer is generally no. Most fish require a varied diet.
Once you provide more information, I can better assist you.