How are minimum tank sizes decided?

[SilkySifaka]

Even since getting into fishkeeping, I've wondered where the minimum tank size numbers actually come from. Early on, I heard of the inch per gallon rule, which although it had many exceptions, was pretty easy to follow. But now I'm just curious where these new numbers come from, especially since a lot of folks seem pretty passionate about it. I've seen fish that are relatively sedentary and stay under 3 inches being recommended in no less than a 30 gallon tank. The neon goby which is 2 inches full grown is recommended in a minimum of 10 gallons on LiveAquaria, and other videos and blogs recommend 20 gallons. Are these arbitrary numbers or is there some science behind these things? What are y'alls take on minimum tank sizes? And what do you use as the ruler (eg LiveAquaria, etc)?

 

[Matt1997]

All numbers come from some keyboard warrior. Just use common sense.

 

[i cant think]

Even since getting into fishkeeping, I've wondered where the minimum tank size numbers actually come from. Early on, I heard of the inch per gallon rule, which although it had many exceptions, was pretty easy to follow. But now I'm just curious where these new numbers come from, especially since a lot of folks seem pretty passionate about it. I've seen fish that are relatively sedentary and stay under 3 inches being recommended in no less than a 30 gallon tank. The neon goby which is 2 inches full grown is recommended in a minimum of 10 gallons on LiveAquaria, and other videos and blogs recommend 20 gallons. Are these arbitrary numbers or is there some science behind these things? What are y'alls take on minimum tank sizes? And what do you use as the ruler (eg LiveAquaria, etc)?

I’m pretty sure they come from experience and max length/activity. So a Tang is much less active than a Blenny. There’s also a great size difference (Unless we need to be scared of mega blennies) so the tank size wouldn’t need to be as big.

 

[MoshJosh]

I think its based on the general consensus regarding a particular fish/organism. It is partially based on experience from those who have kept said fish in the past, partially based on the fish's natural habitat, and partially based on the fish's behavior (and yes, maybe some keyboard warrioring as well).

In my experience the internet seems to err on the side of caution and recommend larger tank sizes while local stores not so much.

 

[monkeyCmonkeyDo]

It's all based off poo and pee bioload.mass to equal parts beneficial bacteria ratios. Lol.
Nah... I'm just kidding.
It's common sense. Smaller fish or open water swimming fish ect.
D

 

[SilvermistInc]

I’m pretty sure they come from experience and max length/activity. So a Tang is much less active than a Blenny. There’s also a great size difference (Unless we need to be scared of mega blennies) so the tank size wouldn’t need to be as big.

You've got tang and blenny switched

 

[i cant think]

You've got tang and blenny switched

I’ve just realised that, oops - Shows how much I need coffee in the morning haha.

 

[Daniel@R2R]

Good discussion. I imagine it is an educated guess based on consensus, but I don't know that for sure. I'd be interested to know where some of the minimum sizes originated from.

 

[doubleshot00]

I’m pretty sure they come from experience and max length/activity. So a Tang is much less active than a Blenny. There’s also a great size difference (Unless we need to be scared of mega blennies) so the tank size wouldn’t need to be as big.

Why does it have to be a tang. Why couldn’t you bring up a red coris wrasse

Imo its based on fish activity and not size. Thats how i base my decision on what I want to add.

 

[LaloJ]

I must base my opinion on the size of the fish in their adult stage, and their activity, after that an adequate tank size should be generated, remember that they have only just begun with fish bred in captivity, so these adaptations or "rules" were made when all the fish were caught in the sea, definitely whoever took out a powder blue tang logically was not going to put it in 10 gallons, but it was possible to do it with a damsel, it's more feasible. You don't build a house for your puppy the same size as you would for an adult German Shepherd. Mention the activity of the fish too, look at those who keep sharks, curved tanks are the choice here due to their behavior, and the size of these fish leads you to logically place them in a very large tank space. Just my point of view and opinion.

 

[JCM]

They are arbitrary. They are general guidelines made to hopefully keep people from killing or stressing fish needlessly. Most are based on previous experience. Jay Hemdal (probably spelling that wrong) put out a pretty good article trying to calculate minimum tank size for certain fish. It's not perfect, but it's an improvement over the arbitrary numbers.

The biggest factors for me when deciding on a new fish: can my filtration handle the additional bioload? Do i have enough hiding spots for everyone to have their own space? Will that species general temperament fit in with my current fish? How much swimming space will that fish need as an adult?

That last question varies considerably depending on the species. I wouldn't hesitate to put an 8" marine betta in a 3' tank, but a similarly sized acanthurus tang would go crazy in that size tank.

 

[LPS Bum]

How are minimum tank sizes decided?​

Haphazardly.

Strictly speaking, even the largest home aquariums are too small, if the litmus test is the ocean. It's really just common sense. If your fish have enough room to swim, eat, and hide, with minimal aggression from tankmates, they're fine.

 

[paparoof]

How far does the fish wanna explore?

I've got a 30 gallon tank. The clownfish virtually never leaves the right 1/3rd of the tank. So that indicates a 10 gallon would be fine for THAT particular fish. The flame hawkfish on the other hand, uses every single cubic inch of water. So though he's only about 2" and Live Aquaria sez 30 gallon min, I have no doubt he'd be happier in a bigger tank, cause he would sure use it.

 

[Flame2hawk]

As a guide I calculate 1 inch of ADULT size per 3 net gallons meaning AFTER water displacement calculation (usually 15%) caused by sand and rocks. I then adjust up or down depending on specimens requirements. Tangs need more space to swim so I find length more important in many ways then total gallons (as long as filtration is adequate), fish comparability, etc etc not an exact science for sure but it’s a process to hopefully get to something that works. Lots of observation needed especially as fish grow larger and generally become a bit more aggressive and territorial. especially true for most tangs and angels. Bullied or bullying fish will ultimately have to be re-homed as once it starts at older/larger adults, it rarely reverses itself.

 

[Reefing102]

As others have said, arbitrary based on experience of the keeper. You can easily house a pair of clowns in a 10 gallon tank for a long while but they will eventually seem to be too large for it.

That said, back in the day, one of my favorite LFS’s used 1 inch of adult fish per 10 gallons. So a clown you’d be looking 30-40 gallons (or possibly more) using that method or at least 80 gallons for a yellow tang. (Combine the gallonage if housing more than one - I.e 2 clowns = 60-80 gallons)

I used the above method for a while, and it never worked for me. My tanks just seemed too empty.

Now, I get what I want and don’t care what others think, though taking into account readily accessible information about the fish and observing them in my tank. No, I’m not putting a tang in a 10 gallon, but by the time I’m done stocking my tank, I believe many would classify it as too small for the bio load.

Now I don’t reccomend this, but fish are not a spur of the moment purchase. Coral, absolutely, but I have no reliable source for good fish locally (without spending an arm, leg, and 2 toes from the other foot) so I can look, research, and then special order and quarantine.

 

[Stigigemla]

When I get questions from my customers of what fishes they can have in small tanks I say that the recommendations from Liveaquaria and similar seems to be for fishes in their selling size.
I usually recommend to have a look att reeflex.net and see what they recommend.
It is a site driven by hobbyists that have had many of the species to adult size.

I was flashed of the change in behavour when I moved some tangs from a 6 foot to a twelve foot 420 gallon tank.

 

[jrill]

Opinion

 

[BroccoliFarmer]

Even since getting into fishkeeping, I've wondered where the minimum tank size numbers actually come from. Early on, I heard of the inch per gallon rule, which although it had many exceptions, was pretty easy to follow. But now I'm just curious where these new numbers come from, especially since a lot of folks seem pretty passionate about it. I've seen fish that are relatively sedentary and stay under 3 inches being recommended in no less than a 30 gallon tank. The neon goby which is 2 inches full grown is recommended in a minimum of 10 gallons on LiveAquaria, and other videos and blogs recommend 20 gallons. Are these arbitrary numbers or is there some science behind these things? What are y'alls take on minimum tank sizes? And what do you use as the ruler (eg LiveAquaria, etc)?

Very simple answer and you are going to have an ah ha moment when i say it.

You go to that peaceful place in your head. You envision your perfect reef tank with everything in balance. All of the fish get along swimming at all strata of the tank. Your clean up crew is 100% efficient. Your corals swaying gently in the current. WOW...Everything is perfect. You cant think of anything else to make this tank more perfect....except...it has to be BIGGER.

You pull out your measuring tape and see how big of a tank you can get. WOW that room is large..you can get a pretty big tank so you choose something in the few hundred gallon range. This is going to be AWESOME!!

Next you have to run it past your spouse. Wow...you never expected her to be that angry over a simple suggestion of taking over an entire wing of the house. So you compromise and go a 'little smaller' and you are in the hundred+ range. This is going to be pretty GREAT!!!

Now, you cost out your new build. WOW...this equipment has really gotten expensive over the last few years and you realize that you have to compromise dream tank size even further if you still want your kids to go to college and you dont want to grab a second job at the local WalMart. So you reality check yourself and realize and settle on something in your budget range. Your spouse is happy, your wallet is happy but your dreams have been crushed. This is going to be OK.

Finally, as you start loading up your shopping cart and the excitement of your build starts growing again after the downsizing disappointments you start rationalizing your purchases. You realize that costs are only going to go up. Eventually your spouse is going to give up and let you do your thang. You realize that your kids aren't smart enough to make paying for that expensive college worth it. The 'the people of walmart' are pretty fun to watch. So you switch out some of your equipment, realize what equipment you can sneak in on a future credit card statement, nudge your tank size up to the hundred+ size again, lie to your spouse about it is the size she agreed to and it only LOOKS bigger and you start your pared down dream build. Life is GOOD!!

And that my friend is the science of Aquarium sizing.

 

[SlugSnorter]

Even since getting into fishkeeping, I've wondered where the minimum tank size numbers actually come from. Early on, I heard of the inch per gallon rule, which although it had many exceptions, was pretty easy to follow. But now I'm just curious where these new numbers come from, especially since a lot of folks seem pretty passionate about it. I've seen fish that are relatively sedentary and stay under 3 inches being recommended in no less than a 30 gallon tank. The neon goby which is 2 inches full grown is recommended in a minimum of 10 gallons on LiveAquaria, and other videos and blogs recommend 20 gallons. Are these arbitrary numbers or is there some science behind these things? What are y'alls take on minimum tank sizes? And what do you use as the ruler (eg LiveAquaria, etc)?

guesses around how big they grow, waste produced, how active they are. take with a grain of salt, but bigger tank is better in this hobby.

 

[92Miata]

As others have said, arbitrary based on experience of the keeper. You can easily house a pair of clowns in a 10 gallon tank for a long while but they will eventually seem to be too large for it.

Kept an RBTA and a pair of ocellaris clowns in a 10 gallon cube-ish AIO (probably about 6 gallons actual display) for years. They did great. Spawned weekly.


The numbers are entirely made up. Some are ridiculously high. Some are ridiculously low. 20-30g for clowns is way more than they need by themselves. 250g for a Sohal tang or 350g for a Unicorn tang are ridiculously small.