Personally I think fish thrive when you cut the 1 inch per gallon rule in half. So 5” in a 10 gal. Don’t get me wrong. I wouldn’t put a 25 inch fish in a 50 gallon long tank because the fish wouldn’t be able to turn around comfortably or if at all. Actually the bigger the fish gets that rule changes. I’d put full size arowana in a 250
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