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Measurements, part 2

Posted 09/16/2018 at 11:06 AM by sacremon

Something that occurred to me at the time I was making my post was a comparison to hard drives, how a drive is advertised as being 400GB but in the computer it is shown as being 372.5GB. Thing is, the situation with aquariums and with hard drives are for completely different reasons.

Hard drive manufacturers define a gigabyte as 1 billion bytes. 1,000,000,000 or 10^9. Computers operate in powers of 2. The way the operating systems are designed, a gigabyte is a power of 2 that is closest to 1 billion. 2^30 = 1024 x 1024 x 1024 = 1,073,741,824. So the hard drive manufacturers and the operating system programmers are using different units from each other. For aquariums to be similar, the aquarium manufacturers would need to be using their own definition of 'gallon' or 'liter' than the rest of the world. In the end, they both come down to marketing.

As an aside, there are some deeper, more technical reason why hard drives numbers can be even less than the differences in the units of measurement, such as the block size defined on the drive and how efficiently that utilizes the space, how much directory space is reserved by the operating system when the drive is formatted and even some operating systems automatically reserving a portion of a drive for low level operations like scratch space for automatic defragmentation (I may be way out of date on that one).

In regards to the use of Total Length for fish, I really have to wonder about measurement of fish like adult male Naso tangs or other fish that have steamers on their tails. Is the length of that streamer included in the reported TL of the fish? How about male swordtails (freshwater)? What about streamers from the dorsal fin like bannerfish and Moorish Idols? Maybe the 2" Pterois radiata I received was measured based on the length of the pectoral fin rays. Makes it all seem arbitrary. Maybe the industry should use Standard Length as the 'standard'. I imagine marketing again is the reason.
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