The "One Inch Per Gallon" rule ........

[Purple]

On various threads I keep coming across the “one inch rule”.

This so called rule suggests that as far as stocking levels go - it’s OK to have one inch of fish per gallon.

So what happens when you have a single 12 inch pl*co in a 12 gallon tank ? - and a 6ft shark sure aint gonna fit into a 72 gallon ........

Kinda blows the rule away a bit doesn’t it - so lets clarify a few things here .........

It kinda works for guppies and neons - but not for the bigger fish - and if you have (for instance) a 20 gal tank with a common pl*co and a handful of guppies - we really get into a grey area. And what about goldfish ? - some say one per 10 gallons - some say one per 20 gallons .... either way, it’s not one inch per gallon - they are far too messy for that.

Some fish can be notoriously territorial too - try a few guppies in a 120 gallon with a Texas cichlid - can you guess which one fish you’ll have left in the morning ?

I can fully appreciate that the vast majority on here already know what I’m talking about - but don’t forget there are a lot of beginners on this site too - and I wonder how many of them take the “one inch rule” at face value as they approach their local LFS.

I figure there are two options here - either don’t quote that rule - or at least try and qualify it, in that it only applies to a tank with individual fish of one inch or less.

If i’m preaching to the converted here - my apologies - to the rest of you ........ the ‘one inch rule” is very specific to the smaller unagressive fish. Don’t take it at face value - always check first.

*celebrate

 

[Fuzz16]

i agree with you
i hear the one in/g rule to often with bigger fish.
perhaps you could post up some fish with thier different gallon rules to help out those looking for what they can put in thier tanks and what they cant.

 

[CAPSLOCK]

I agree whole-heartedly that it isn't often qualified enough. It's really just a rough guideline anyways. Plus, lots of people don't realize it goes for the adult size of the fish, not the little 2" common pleco that they have now.

However, that rule does work with goldies, since they get to 12" or so, 10-20g per fish is right within the 1"/gal rule.

Oh, and it REALLY doesn't work unless you're doing freshwater...

 

[Guysy1110]

I dont think the 'one inch per gallon' rule can apply to many fish these days, most fish need the room to "stretch there legs" and maybe also so certain fish can claim there territory in the tank.

But like capslock said, the rule does often apply when the fish are goldies.

 

[cchase85]

I agree whole-heartedly that it isn't often qualified enough. It's really just a rough guideline anyways. Plus, lots of people don't realize it goes for the adult size of the fish, not the little 2" common pleco that they have now.

However, that rule does work with goldies, since they get to 12" or so, 10-20g per fish is right within the 1"/gal rule.

Oh, and it REALLY doesn't work unless you're doing freshwater...

I'm looking at my 20 gallon right now and picturing a footlong goldfish in there.

I don't think so

 

[VirgoWolf]

I agree, I think the 1"/gal rule only applies to freshwater fish under 4" that are not messy, not aggressive, not territorial, and not overly active.

Personally I don't think any goldfish is suited to live it's entire life in a 10gal tank, MAYBE the smaller fancy goldies in a 20gal, but I coulden't keep a commet or something of that size in anything smaller than a 55gal, and then I'd say 2-3, tops.

 

[bigredspecial]

I agree 100%... not to mention that a single 12" fish probably has the same amount of biomass as 50-60 1" guppies... people don't realize that as length goes up, so does height and width by a proportional amount.


I rate this "rule" up there with the "fish only grow to their environment" bull****.

 

['-JIN-']

definately dont agree with this rule.discus can grow up to 6"-8" but they need a bigger tank.

 

[TX8balls]

when youre talking about discus' though you need to take the diameter of the fish adn divide it by to to get the radius (r) then plug it into the formula
(pi)r ^2 and then apply the one inch per gallon rule

 

[bigredspecial]

hahahaha... stocking by area... that's hilarious!


Then again, maybe you're on to something... instead of length/volume, maybe we can go by volume of fish/volume of water? cubic inch of fish per gallon??

Vf/Vw????

Hey, at least it makes up for the biomass difference. Now if it would only people would realize fish need to be able to swim more than their own body length...

 

[FroggyFox]

don't forget to add surface area of the tank, if you're doing that bigred not necessarily volume. At some point oxygen is a valid commodity too...if you have a 15g tall regular hex, it will have to be not only stocked with fish that will be ok for the tank size wise with its height orientation, but lower than a 15g with a normal footprint because of the smaller surface area.

In any case, Purple brings up a great point that we all need to remember. Before you just randomly spout out about the one inch of fish per gallon rule, we need to qualify it.

I would say though that for most freshwater COMMUNITY fish that stay under about 4 inches...the rule is pretty good to go by, especially for someone who's just starting out and want to know how many tetras they can put in a 20 gallon tank.

Also, if you're going to split hairs on someone's stocking plan, take it easy and take it slow. Remember not everyone has the knowledge that you do. MFT is to HELP us all learn how to better care for our fish, not to show off what you know eh? Simply telling them "you're overstocked." and leaving the thread is not cool.

 

[bigredspecial]

That's an excellent point about surface area; As a matter of fact, when I first got into fish keeping, I had a book that said to go strictly by surface area, and that is what I went by. It even worked out to my benefit, as I had a 15 long at the time, so I put more fish in there than I would have using the inch per gallon rule. Keep in mind, that only worked because I was stocking it with small tropicals, and had an obscene amount of filtration on there.

I thing the big thing that is required isn't a 'rule' per se, but a bit of common sense. A rule can calculate the bio load, but people should be able to judge if the fish will have room to swim as well.

 

[Fishywishy]

surface area is better, think I read it as lenth x width then divide by 12. I think in a standard 55gal kit from walmart that gives you 52 inches of fish (full grown size)

when someone says you're overstocked and leaves a thread, it's usually because you're overstocked on so many levels it's untrue. overstocked based on swimming room, overstocked based on full grown size, overstocked based on the basic rule (back to your one inch per gal rule), overstocked based on filtration, overstocked based on care .......etc. I think I see overstocking more as an issue of swimming room or gas exchange (a larger surface area tank is going to have more exchange) then bio-load

the only solution is to get rid of some fish, so the long time people here just say "overstocked" and leave...... poster was looking for a solution, poster got a solution (it just wasn't what they wanted to hear LOL)

 

[FroggyFox]

the only solution is to get rid of some fish, so the long time people here just say "overstocked" and leave...... poster was looking for a solution, poster got a solution (it just wasn't what they wanted to hear LOL)

Um, no that is the problem. Telling someone that they're overstocked is a statement of the problem, not a solution to that problem.

New people don't KNOW about the different ways they can be overstocked so it might not be completely apparant to them. For instance 5 little goldfish in a 20g tank might LOOK fine! But for those of us who know something more about the nitrogen cycle, we know that those five little goldies are quickly going to start making a large mess of that tank.

 

[bigredspecial]

&Yep, that's the same rule I used to use(or close to it).

I agree with you though; Bio load shouldn't be the main consideration, as it can be taken care of with larger filters and/or more waterchanges(to a reasonable extent). Swimming room, gas exchange, and room for territories can't be helped.

 

[James From Cali]

There is other things needed to take into consideration aswell. Plants contain an important role in stocking as well. They give out oxygen but take up room. Some fish prefer more swimming space over others. Also the levels the fish swim in as well can determine if your overstocked or not. The main thing to look at is filtration and sizes of the fish and water changes size/schedule. Currently my tank is stocked with 5 Neon Tetras and 2 Male Platys. I am planning on getting a Betta and 3 Panda Cory's. I have plants in the tank which add oxygen and I am going to be upgrading my filtration. I do weekly 30-50% wc'sand things go great.

 

[christinap]

Good info in there, thanks!

 

[Cas]

I use this rule for my tank because the biggest fish I have is only 2" long, btu no I don't think it would work with the larger fish.

I think someone should put up an FAQ or a guide or something to give newbies to the Fish Tank world some help and guidance when it coems to stocking there fish tanks.

Cas

 

[Fishywishy]

Um, no that is the problem. Telling someone that they're overstocked is a statement of the problem, not a solution to that problem.

actually, niether one of us are correct. It's not a statement of the problem (that's what the original poster was looking for help with), it's actually a statement of what is causing the problem. and if you want to get real technical, when someone posts a problem are they looking for the cause or the solution? because if they are looking for the cause, they can find the solution..... but if they are looking for just a solution, why explain the cause? (and I really am smiling while typing this so don't think I'm just arguing to argue, or getting in your face.....it's more a play on words and YOU started it LOL)

The solution is still the same.....get rid of some fish or get a bigger tank (common sense tells us this), but I do agree with you it would be helpful to send them on the right track of getting rid of the right fish, or what size tank they need. but then again that's why people started using general rules ......which started this whole thread! (I wasn't meaning to disagree with you, I just understand why some experts just say overstocked and leave it at that. not being helpful, is seeing the problem and not saying anything at all.)

I think people are using the "one inch per gallon" rule as a way of not saying something rude like "holy crap, would you like some water with your fish?" The inch per gallon rule is a way of giving a general idea of just how far overstocked that person is and a way of getting them to research what they have in their tank and what are appropriate stocking levels, all rules that use inch per whatever are referring to full grown size, which leads people to research their fish. Certainly don't want to see anyone discouraged from helping or trying to help another! You have to start with something to point others in the right direction.

and James, makes a really good point you can really push limits with live plants, but I think I would describe the benefit of live plants differently as far as stocking goes... I never really saw plants as big oxygen producers, but really big nitrate consumers (final product of fish waste)

 

[James From Cali]

actually, niether one of us are correct. It's not a statement of the problem (that's what the original poster was looking for help with), it's actually a statement of what is causing the problem. and if you want to get real technical, when someone posts a problem are they looking for the cause or the solution? because if they are looking for the cause, they can find the solution..... but if they are looking for just a solution, why explain the cause? (and I really am smiling while typing this so don't think I'm just arguing to argue, or getting in your face.....it's more a play on words and YOU started it LOL)

The solution is still the same.....get rid of some fish or get a bigger tank (common sense tells us this), but I do agree with you it would be helpful to send them on the right track of getting rid of the right fish, or what size tank they need. but then again that's why people started using general rules ......which started this whole thread! (I wasn't meaning to disagree with you, I just understand why some experts just say overstocked and leave it at that. not being helpful, is seeing the problem and not saying anything at all.)

I think people are using the "one inch per gallon" rule as a way of not saying something rude like "holy crap, would you like some water with your fish?" The inch per gallon rule is a way of giving a general idea of just how far overstocked that person is and a way of getting them to research what they have in their tank and what are appropriate stocking levels, all rules that use inch per whatever are referring to full grown size, which leads people to research their fish. Certainly don't want to see anyone discouraged from helping or trying to help another! You have to start with something to point others in the right direction.

and James, makes a really good point you can really push limits with live plants, but I think I would describe the benefit of live plants differently as far as stocking goes... I never really saw plants as big oxygen producers, but really big nitrate consumers (final product of fish waste)

Good points. And why I say that the plants produce a good ammount of oxygen is during the process of Pearling they take off with oxygen bubbles and continue to make oxygen. Also consuming Nitrates is big. Which in the end you might need to supplement them if your fish arent producing enough, but in an overstocked tank that shouldnt be a problem. I am going to say this though, with live plants/great filtration/proper wc's/proper research you will get a nicer/healthier tank and happier/healthier fish.