What are your thoughts on the 1":1 gallon fish rule?

One thing that you will learn after some experience with aquatics is that there are no rules, just guidelines.

The 1"/gal Guideline is such a misquoted phrase. It is like saying the entire right turn on red law is "yes, you can turn right on red". The law states after coming to a complete stop, and yielding to traffic & pedestrians. Try doing some right turns on red only going by the first part, see what kind of trouble you get into.

The same goes for the one inch per gallon guideline. The complete guideline is "one inch of slim bodied fish that grow to no larger than three inches, per gallon of water". This guideline is to keep newbie aquarists out of trouble, many experienced aquarists double or triple this stocking.

Nothing really use-full to add I'm afraid, but i will say this. I have had many fish and tanks and i think as a rule the 1:1 rule is not the best thing for fish. Most fish need a much bigger tank than that math allows to be happy. You may find for some fish this works but size isn't as important as habit or what the fish likes to do. I think buying bigger tanks than needed is a better rule of thumb. Also filters and bio filtration play a big role. I look at it like this, If I had to spend my life in a glass box I would want it to be a nice sized one vs. a just big enough sized one. TTYL

It depends on the size and kind of fish you want. The first two suggestions above me sound good. Do not follow the one inch of fish per gallon rule. No gold fish. The fish you keep should be small and remain small not growing more than ~3 inches. Guppies, zebra danios, platies, neon tetras, white cloud minnows are some good choices (all about the same size) 8-10 would be a good number. If you decide to get schooling fish, please get at ~6 of them.

It depends on the fish as if you get a fish that is 5 inches but is very active then I would say it should be in a 20 gallon tank. While if its a 5 inche fish that doesnt move then a 5 gallon would do.

As I've said in many of my answers, this rule should be totally disregarded. A perfect example is a 10 gallon tank-- you could easily put 10 Neon Tetras in it, and probably have room for more. This would be an understocked tank, which isn't necessarily a bad thing, but it shows fault in the "rule". Take that same 10 gallon tank and try putting a 10 inch Oscar or Bala Shark in there-- NOT A CHANCE! They wouldn't be able to turn around in that tank, the Oscar would die of ammonia poisoning in days, and the Bala Shark would probably last about 10 minutes before jumping or flying into the tank walls.

The "inch of fish per gallon of water" system only accounts for two facets of stocking-- size and volume. It entirely ignores waste production, aggression, activity, swimming level, schooling habbits, pH (which affects ammonia toxicity), temperature (which affects the amount of oxygen in the water), surface area (also affects the amount of oxygen in the water), general dimensions (tall tanks hold less fish, as fish swim laterally, not vertically), girth, filtration, maintenance, and loads of other factors that I haven't even thought of yet.

If you can apply this "rule" with common sense, it would require totally disregarding the "rule", as it rarely works. It was just created as an easy way for pet store employees that don't know fish to "help" their customers, and now it has become a plague of epic proportions.

Well goldfish and koi are generally dirtier fish so its best to give them a lot of water toreduce the chances of nitrate poisoning. I generally stick to the 1:1 ratio and have no had much problem. However, I always have more water per fish generally so they have more room to swim and I find the larger the aqurium the nicer it looks and the easier it is to clean. If you have a betta I recommend about 2-4 gal. of water per fish. Any less than that they are not really all that happy and more prone to fin rot if their water is not cleaned regularily.

well according to that rule some of my guppy tanks are very overcrowded! however I have filters with a large surface area and do 25% water changes every week and my water tests fine-like has been said some fish are messier than others.

i think is bull, the one gallon rule doesn't specify the size of the fish you know, i have really small fishes in my tank and they are schooling fish, so base it on the size of the fish you want to have. and also what activity the fish does, like if they are lazy, or they are like playful.

Its always worked for me. I've never had problems with over stocking.