| Oie, good question, I'll leave the average growth rate for someone else, cause honestly without locking down a species i couldn't tell you.
There's plenty in the family & especially when your talking an enclosed environment a great many factors matter, some will require great light & love being high, some will love great light & happy to be shaded, others prefer low light & high flow, others prefer high light with low flow, plus couple that with the type & regularity in which you gross feed them & the space in which they have to colonize will dictate your question, or someone can tell you about 3inchs a year..lol
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