Last thought, a quick example;
Say i have a large tank with one wild cod, dont know what size maybe someone could recommend the right size for a wild cod, I'm guessing quite large. This wild cod I keep for a 6 months/year fattening it up. I take it out and sell it as cod for chips in a shop, from one fish I have two servings. Each serving costs the customer £5, I sell it to the shop for £3 each.
The running of my tank and food and lighting and electric, filtration, salt. Would be alot more than £6.
Therefore I would need to keep a far greater amount of cod in one tank in order to pay for their keeping. I would be giving them sub-standard conditions, or face not making any money at all and being in financial ruin.
In the same way,
Say I catch lobster for the local market. I have to catch say 30 lobster a day in order to meet my requirement otherwise I won't have enough money to cover my costs for fishing and selling.
I fish for 10 hours a day which means I have to catch 3 lobster an hour in order just to be able to go out and catch lobster the next day. In order to feed my family pay for my food any stupidly large wild cod tank, I need to catch an extra 3 on top of my minimum, so I have at least 90 per day.
So now my hypothetical daughter wants an iPod. Which means I need to catch even more. But in a 10 hour day I can't physically catch humanely and check every single lobster. So I catch a net load every hour, collect them for the market and make my money, otherwise I will face financial ruin and my hypothetical daughter will hate me for not getting her an iPod.
Jut a thought. Lol