Join Date: Dec 2010
Location: Ontario, Canada
If your book is correct, you could keep one 16" fish in a 10G tank. Now, that doesn't make much sense, does it. Whereas, 16 neon tetras might be ok assuming you were extremely vigilant about cleaning and had extra filtration.
Actually, the 1inch per gallon rule is really not a good rule to use literally. As a general guideline, perhaps, but..I wish people would forget that rule completely...we know a lot more now than in years past. It makes people just getting into the hobby more likely to overstock and not be prepared for the maintenance required.
Ammonia levels isn't the only thing to keep in mind. It depends on the type of fish, their schooling habits, whether they are friendly or not, what area of the tank they occupy etctec.
In cichlid tanks, for instance, over stocking is quite common to cut down on the fighting. In cases like that, you would need much more filtration than that tank is rated for.