Just Out Of Curiosity...

your1stopshop · Dec 14, 2008

I have a question about this one inch of fish to gallon of water business. Now I know this is a guideline, and is only useful for slim fish under 3 inches, this post isn't to start a long discussion where everyone points out reasons the guideline doesn't work, and then someone always says "its not a rule. its a jumping point for beginners" and in the end everyone agrees that stocking is as much art as science, but only after someone has come up with some extremely complicated "rule" about stocking that is obviously "better" then the 1 inch per gallon "rule". Sorry went off on a tangent. Anyway my actual question, is where did this come from? Is this rule based on the idea that a 10 gallon can only have enough area for bacteria to grow on to hold "10 inches" of fish? If thats the case couldn't you just add decorations to increase the surface area? Or is it that in 10 gallons after "10 inches" of fish the nitrate builds up to quickly? Which could possibly be remedied by frequent water changes? Or possibly that the surface area of the tank only allows for enough gas exchange for "10 inches" of fish? Which the use of a spray bar might fix? A combo of all 3? I was just curious, thanks

JustKia · Dec 14, 2008

I believe that they are all contributory factors as well the area a fish needs to be able to swim at a normal pace, turn, etc.
There's also the growth hormones that some fish give off to factor in.

If you have very good maintenance, very good (over) filtration and wisely choose your fish then it is probable that you could "overstock" with no obvious detriment to your fish.

drobbyb · Dec 14, 2008

JustKia said:
I believe that they are all contributory factors as well the area a fish needs to be able to swim at a normal pace, turn, etc.
There's also the growth hormones that some fish give off to factor in.

If you have very good maintenance, very good (over) filtration and wisely choose your fish then it is probable that you could "overstock" with no obvious detriment to your fish.

Not only those but also there is a limit to the amount of oxygen that the water holds. Also something should be said about the fish waste vs. the volume of water. Remember, the solution to pollution is dilution. With more water the concentration of waste is spread around more.

There is also the argument that a 10 gallon tank should hold 10 inches of fish, yet if you try to put in a 10 inch fish, the tank will fail miserably.

Therefore, it's only useful as a guideline.

Tolak · Dec 14, 2008

Where did this come from? Hard to say, it goes back at least as far as the early 60's, perhaps earlier. I've got some old magazines I could flip through, probably get some idea how far back it goes.

It probably comes from a retailer sick of replacing dead fish.

your1stopshop · Dec 14, 2008

Tolak said:
Where did this come from? Hard to say, it goes back at least as far as the early 60's, perhaps earlier. I've got some old magazines I could flip through, probably get some idea how far back it goes.

It probably comes from a retailer sick of replacing dead fish.

That's probably a logical conclusion. I always thought it was something that someone wanting to reduce fish suffering would have advised, but its probably more likely a business wanted to reduce losses (and give easy to remember information to part-time employees) would have concocted.

OldMan47 · Dec 15, 2008

Tolak, I know it goes back to at least the early 50s. Even then it was treated as a rough estimate for small fish only. The real holding capacity, all silly simplifications aside, is determined by how much oxygen your water can hold and exchange and how well you can remove pollutants. If you had a small cage that only held a gallon of water but replaced the water in it with clean oxygenated water every 10 minutes, you could keep lots of large fish in it. The limiting factor would then be compatibility and the fish's ability to actually live that close to other fish. We don't replace all of our water fast at all and we rely on the filter to clean the water and the water surface to replace the oxygen so we hit limits on stocking very much earlier.

mike os · Dec 15, 2008

I am not sure there is any real "reason" for it, in scientific terms..... ie O2 level, space etc. I think it is simply an observation by experienced aquarists of what generally works without too much trouble or work.

Given that until relatively recently it was the smaller species that were generally kept ( costs.... equipment, shipping etc) this was a very useful rule of thumb. For those keeping larger or more difficult species.... well they generally had the experience of keeping small fish & learning the hard way, no internet or books...well not many.... & astronomical cost of larger/rarer fish....IIRC medium cichlids cost about the same as they did in the 70's, (discus, dempsy's etc) but wages have increased astronomically since then.. & yes I have been keeping fish that long.