"Don't let a limited amount of space or money keep you from setting up a saltwater aquarium"
"Dealers are likely to realize higher profits on larger aquariums, both from the initial setups and from the subsequent stocking of increased numbers of animals in these tanks."
Most advice against nano tanks comes from experienced hobbiests. And the lfs that recommends against it probably doesn't want to see everything the noob buys die.
"Perhaps the most compelling reason why large aquariums are so strongly recommended is that it seems as though a large tank should be inherently more stable than a small one in terms of water chemistry."
This guy can refute this fact all he wants, but it is an absolute truth. And a begginer needs all the stability they can get to offset the mistakes that will invariably occur.
"Common wisdom suggests that detrimental environmental changes will occur more rapidly and with much more severity in small saltwater tanks. The assumption is simple: Because these smaller tanks contain less water, toxic organic wastes, such as ammonia and nitrite, will accumulate at a faster rate. This is true, however, only if the weight of the animals per gallon of water (and per unit filtration efficiency) in a small tank exceeds the ratio found in a larger tank. If the ratio of animal weight (more correctly, biomass) per gallon of tank capacity is identical for both size tanks, then the build-up of toxic substances will occur at the same rates and in the same proportions. That is, 1/10th gram of ammonia in a 10-gallon tank is the same as 1 gram of ammonia in a 100-gallon tank."
Wow, if ammonia only enviromental difficulties to be had, I might agree with this.
"Water temperatures are less stable in a small aquarium. Given two tanks of widely differing capacities, such as a 10-gallon tank and a 100-gallon tank, if the heater in each one should cease to function, the temperature in the small tank would drop much faster than in the large tank. This is perhaps a minor point, because the tank temperature can drop only to the room temperature, and this is not fatal to most organisms unless the temperature remains low for a substantial amount of time."
Temparature is a minor point??? What happens when they realize they need more lighting to support the corals they just got? He doesn't mention OVERheating, which is the more common trouble.
"My own experience with small marine tanks started almost 30 years ago. It was a 15-gallon aquarium that I paid for using money earned from a paper route."
Wonder how that worked out? He doesn't say, does he?
OK. Enough knocking the nanos.
Most of us do not recommend them for begginers because most begginers do not realize what they are getting into to begin with.
Most noobs think they need salt and different gravel, and voila! Some are doing a 15gal, because they "got one for free", or something similar. I usually discourage the determination of startout tank size by using "what I had lying around". Simply because by the time you buy all the additional hardware needed to operate a marine tank successfully, the tank is the cheapest investment.
Nanaos can be done, and look stunning, but should really be attemped after one gains knowledge in the hobby.
GL