1 Inch per Gallon Stocking

The 1 Inch per gallon rule has very little to do with what species, aggression, or any of the other factors that some people use to guage the amount of fish in their tank tanks.
The more relevant method of stocking a tank is to calculate the surface area of the water to air interface, as this is critical in determining the amount of dissolved Oxygen needed to support life
I have always employed the following, for Tropical Freshwater Tanks
For every 1 inch of adult fish length to be stocked, a surface area of 12 Square Inches is required
Overcrowded and over stocked tanks not only look bad, they are a recipe for bad water conditions, disease, and poor filtration

Very insightful post, but in planted aquaria plants provide oxygen, could that hinder your calculation? And I just threw in your SA equation in and it came with 31 inches of fish for my 29.

 

This formula is a widely recognised method of stocking, and I personally have use it for many years
When I first started keeping fish some 30 years + ago, no information at all was available, and I gleened this info from reading books about 15 years ago ( no www. then for me ), and I have used it with great success since.
As for the plants ? , the amount of oxgen they give up is minimal in comparison to the tank water/air interface.
the water / air interface can be increases very slightly in any tank but introducing a ripple on the surface.
However, the inclusion of an air stone will not add any significant amount of air into the water - its the ripple it makes at the suface that will do that.

 

thanks, ill be sure to drill holes on the top of my spray bar to create surface ripples sometime (off topic sorry)

 

I use it as a general rule as that's all I know; however, I have four Bolivian Rams in a 75-gallon tank ( I have other fish in the tank of course, but the Rams are unphased by them). Each Ram seems to have it's own section of the tank and for the most part they don't try to kill each other and respect their areas ( I think I ended up with 3-males and one female, go figure). I would be hard pressed to really add more regardless of "the rule" based simply on the fact that they seem to need a bigger house and are really territorial.

I'm slightly overstocked in my 20-gallon using "the rule" but I have a really good filter and I change 50% of the water weekly so I think I'm good.

 

I think at least for beginners it should be a rule, but I think those of you with more experience probably know what works and have your own methods. So maybe "for beginners we SUGGEST one inch of fish per gallon" would be a more appropriate way to put it. It doesn't take into account filtration, live plants, oxygenation, etc, but a beginner is probably just learning these things so better to err on the side of caution

 

The 1 Inch per gallon rule has very little to do with what species, aggression, or any of the other factors that some people use to guage the amount of fish in their tank tanks.
The more relevant method of stocking a tank is to calculate the surface area of the water to air interface, as this is critical in determining the amount of dissolved Oxygen needed to support life
I have always employed the following, for Tropical Freshwater Tanks
For every 1 inch of adult fish length to be stocked, a surface area of 12 Square Inches is required
Overcrowded and over stocked tanks not only look bad, they are a recipe for bad water conditions, disease, and poor filtration

I would agree with you fully on this, but for the fact that the 1" rule and the absolute importance of surface area were first cited in the early 20th century by guys like Innes, and even he says that he is speaking of totally unaerated aquaria when he speaks of surface volume and stocking. To put that in perspective, under lighting, he advocates incandescent lighting for 'those not afraid of electricity'.
While I believe that I mentioned in another post that I stand in awe of what the early aquarists accomplished, given their resources, it is also true that they would barely recognize a modern aquarium, or at least its equipment.
As for the question asked by Cygnus, I tend to stock by adult size, even when stocking juvies, and take the various attributes of the fish into account (i.e. mass, activity, diet and manner of eating-an oscar makes a pig look like a genteel eater-, aggression/territoriality).
My basic indicator of stocking comes from my water parameters--nitrates persistently too high, lessen bioload, nitrates low, room for another fish, perhaps.-------rick
BTW, I believe that stocking levels do effect aggression, especially in large cichlids; a friend had two oscars in a 50 gallon tank, of all things, and they would consistently kill 12" plus plecs--when put in a 150, they became model citizens.

 

https://www.fishlore.com/aquariumfishforum/threads/one-inch-per-gallon-rule.36789/

Ken

 

I think in terms of the amount of territory and if they aren't territorial, a common sense amount of personal space for each fish. My tanks are almost always understocked by whatever means someone uses to guage it. But I would feel comfortable technically overstocking a tank with a good mixture of bottom, middle, and top level swimmers that are not competing for space. Having 10 platies and 10 cories in a tank is not the same as having either 20 platies, or 20 cories even though the bio-load is nearly the same in all three cases. In any case you need to perform whatever amount of water changes necessary to keep good water parameters.

 

Trying to be a rebel over here saying "I don't believe in rules" :;br This is biology after all, with a good bit of ecology mixed in, and rules are hard to come by. The one inch per gallon rule is pretty pointless in my opinion. Take two hypothetical fish, one in only 2 inches long and is what's called a "rover predator" The fish is stream lined, powerful, and only uses the middle level of the water column; it never stops moving. Fish two is 6 inches long and is what's called a "lay and wait predator" it is considerably longer than the first fish and is not as streamed lined; its much fatter. This fish sits in a plant, a log, any suitable hiding spot all day and rarely moves. Even though the first fish in the example is smaller, it needs a much larger tank than the bigger fish. Feeding habits, activity level, as well as the ecological presence each fish has needs to be considered over simply how many inches the fish is. Is it a shoaling or schooling species, they both have different size requirements. Understanding the physical morphology of the fish is just as important. By simply observing the physical characteristics of a fish we can determine a great deal about its swimming habits as well the type of environment it was originally found in. The footprint of the tank in my opinion plays a larger role than the gallons of water it contains. A 3 foot long by 1 foot high tank is going to be better suited for most species than a 3 foot high by 1 foot long tank would be. Think 20 gallon long tank vs 20 gallon tall, they hold the same volume of water but the 20L can hold a greater variety of fish.

 

Rules are ment to be broken, challenged and brought to light. If we all followed the rules then we would never find new ways of doing things, we would never challenge ourselves. Always excepting that what is written is truth.

I follow all rules as a guideline. Plus lets not get Laws mixed up with Rules. By the rules we change our water to lower nitrates, the law of the nitrogen cycle says nitrate built up will kill your fish, so change the water. That's a law, not a rule. Laws are facts..Law of gravity for example..I'm still trying to break that one.

 

I only keep little fish that don't exceed 10 cm.
But just to play it safe I use 1/2 an inch to a gallon so my fish have much more room.

 

There's a good example Harlebleondora. By the 1 inch rule I could have 125 penguin tetra's in my new tank.
That would be kinda cool.

 

Absolutely ridiculous..

 

I don't go by this rule... Say a male guppy... If you wanted just one and was going to keep it in a one gallon tank imagine the uproar it would cause. Also the bioload plays a big part, and the fish temperament. I think its finding a balance between what works to make everyone happy.

 

I throw that rule completely out the window, and don't even consider it when I am stocking a tank. But in my head I can picture most common species and how they will look and act. Even with new species, I can look at their profile and compare them to another fish with similar characteristics that I do know about.

But to someone who has never kept fish, it is a valuable guide. Using it will tell them that they can put 4 platies in a 10 gallon tank, where otherwise they might try to put in 10. In fact they won't be too far of the mark with most common small fish found at their LFS. Usually when they get into trouble is because they don't realize how large the adult fish get (goldfish, cichlids, plecos, etc) and not because of the rule.

 

Duplicate post

 

It's not a rule. It's a guideline. And it only works with your typical starter aquarium fish (the ones that should be starter, not the ones that Petsmart tells you are starter), pretty much guaranteeing people don't overstock a 20 gallon with small fish. Move on to oscars or plecos or goldfish or any oddity, and it doesn't work.

 

It seems that every so often we get into a conversation about the 1 inch per gallon rule, so I figured it would be nice to see who believes it, who uses it, who somewhat agrees with it, and who flat out doesn't believe it.

I don't recommend it for any fishkeeper, newbie or experienced. I don't consider it a "good place to start" because there are too many exceptions and variables for it to be considered a rule. It's more a rule wannabe. Not to mention that having a rule like this doesn't lead to the fishkeeper doing species research.

I would much rather give advice based on specific stock in a specific tank size. Solid information will lead to a more successful fishkeeping experience.

 

its a bad rule it doesn't take into account the activity schooling needs or temper of the fish plus fish arn't flat creatures so it mathmaticlly is very stupid to me that anyone (not to offend you) would always use it. I can get if you are starting out and have made a mistake I mean I have to admit I have used it and it caused a big problem (a 7" convict doesn't belong in a 10 gallon tank) I was very miss informed so people please do your research and if you need a rule I say to be safe use this one 5 gallons per inch of full grown fish and this is only a starting point please research

 

Lollipopkiller- and the ones who are more flat, like Angels, are fairly large from top to bottom in relation to their length, I've noticed.

 

ya not really a one dimentional creature

 

But then if you wanted group of 6 neon tetras that would mean you needed a 30 gallon tank if we went by your advise :L

 

@lala What are you referring to?

@lollopopkiller housing a 7" convict in a 10 gallon is more relatable to a lack of research than ineffectivity of the 1 inch rule.

 

Lollipopkiller said in a post to stick to the 5 gallon to one inch of fully grown fish.

 

If you are going to use measurement as a guide, either mass or volume would be better. Unfortunately it is rather difficult to measure the mass or displacement of a fish and no one publishes this kind of information for adult fish.

 

I just said it to be safe and I also said research but its better to go big than to have a big fish in a tiny tank and I did my research the thing grew bigger than it was supposed to... and neons in my opinnion should be kept in a bigger sized tank for more swimming room

 

Going by total volume dosen't always work either (IMHO). According to this rule, then my 150 gallon is WAY too small for my 3 oscars ! 14" L x 8" H x 2 1/2" W = 280 sq in x 3 oscars = 840 sq in, so according to the total volume, I need to get at least a 840 gallon tank ?

I don't really mean for you to need to calculate the actual volume, sorry I should have been more discriptive, there is a better way to find out the tank size required for a fish. Take the legnth of the fish and add the width to that length. That should give you a more approximate tank size guid line. (Sorry for the late reply)