The Importance of Proper Numbers/Stocking

I know that most of us are aware that there are ideal stocking levels for certain types of fish. For example, tetras are best kept in numbers above 6 as they are social swimmers. Some cichlids, although I'm not up on this at all, need certain male to female ratios to curb aggression. I have experienced this first hand with my Rummynose and Columbian tetras. The more I have, the happier they seem, more active they swim and more vibrant their colours are.

Recently I had to euthanize one of my male Rainbows, which now brings me down to 1 M and 2 F. The fish that I had to put down was a male. Since the loss of the male, the other male is SIGNIFICANTLY less colored up and no longer flares his fins and the other male in a battle for dominance.

The point I am trying to drive home is that without proper stocking numbers, you miss the natural and truly wonderful behavior of the fish. This also applies to overstocking a tank. If there isn't adequate space for their natural behaviour, you'll miss it there as well. Listen to the experts, do your research and you will be rewarded with the proper personality of your fish, which in my humble opinion, is much better than the odd fish looking lost and merely existing without friends/in an overstocked tank.

Over the years, I have developed an unorthodox stocking rule. You can't use one inch per gallon, as an inch of goldfish and an inch of neon are radically different weights. So I figure you calculate how many fish you can have using whatever method you think is sensible, and put in way fewer than that. Very scientific....
But I also figure you should try to be certain your tank is ten times the length of its occupant's maximum adult size. That's a behavioral/fishwatching rule, and it really pays off.
Make your tank for your fish. You may have to read up on the fish and use youtube to look at where it is from, but it pays off.
Someone recently asked me if she should get Rasbora heteropmorpha. I wrote back and explained that it was a beautiful fish if it could move from shadows to light, and that it needed Cryptocorynes or amazon sword type plants along the bottom, or its colours and behavior would be dull. The person contacted me to complain the fish I suggested and she bought were boring. I asked how her plants were doing, and the answer I got was:
"I asked you about fish and not about plants. I don't keep plants".
Doh.
You have to look at a fish as a result of a very complex interplay of water, environment, temperature, and social behavior, and set up to maximize your (and its) experience. Some fish need to be in groups. You can't cheap on that. Others are solitary.
This remains a reader's hobby, and both reading and our fish can give us a lot to think about.

I knew you'd have something to say here, Gary.

In regards to the person who only took half your advice, "you can lead a horse to water....".

Bottom line, research and tips from people who have experience are worth their weight in gold!

I can comment on Goldfish/Koi in that they are very social creatures in that they prefer to be kept in groups. Single or a couple of fish look lost and hide in corners. groups spread out and make themselves at home. That is actually something to kept in mind when your quarantine fish. They like company and you should include one or two of your own fish if it's just one in there.

Steve