My flagtail is a GREAT algae eater. Someone posted here they don't do so good after a certain size, but that was the first I ever heard of that. Mine is only around 9" so has a lot of growing to do. He grew about an inch a month so far. They can be slime eaters just like pleco's so be aware of that. I think they are a great looking fish. It is my wife's favorite fish and I had to get rid of one that was harassing it.
It's isn't so much that they don't do well after a certain size as it is that there are reports of going after slime coats and refusing to eat algae when they get larger. But it all varies. Fish have different personalities just like people do. I know people with 13" flagtails that wouldn't hurt a fly and I have read of 7-8" flagtails who go after the slime coats of their tankmates.
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