Swimming ratios

[Krypt]

It's the holiday season, and as people get into the hobby or start looking to spend their christmas gift certificates, I've noticed an increase in threads on several forums about, "What size fish for my tank" stuff. They've been getting the usual responses, 6ft for tangs and large angels etc.

But all those threads got me thinking, why is that? I know it's supposed to be for optimal growth and to prevent stress and stunting, but in mathematical reality, it seems wrong. Hear me out for a second.

Say you have a 3 inch Blue Tang in a 72 inch tank. Now we all know that tangs are linear swimmers, they like swimming in straight lines in open water. Now say that the 72 in. tank is completely open, that Tang has a size to space ratio of 1:24, meaning that for every inch of the fish there is 24 inches of swimming room. But as the fish grows, that ratio becomes smaller and smaller. If that tang grows out to an adult size of say 10 in., then the ratio drops dramatically to approx 1:7. That's not alot of space for a swimmer that can whip through the water.

What I'm getting at here is, if 1:7 is acceptable for an 10 in. tang, why isn't it acceptable for a 3 in. tang? I know the most likely answer is stress/stunting, but if that were the case, then why wouldn't the bigger tang suffer from the same stress? Is it possible the 6ft tank rule is just being used to ensure the fish has the right space as an adult?

 

[Nu-Nu the eel]

My opinion is that it doesnt work for the 3" tang, because if the ratio for him at that small of a size is 1:7, when he gets bigger that ratio will be dramaticaly smaller. Nobody should buy a fish if they can not provide the right size tank, enviroment, or life for that fish for its whole life. What i mean by that is most people say "i will rehome the fish" or "i will just upgrade to a 180 later" well people become attatched to their fish and dont get rid of him, and they cannot see how much he is growing so they dont realize the tank is too small when hes at adult size.

 

[Krypt]

So what your saying is that the 6ft rule is a preventative for the inexperienced and to ensure the fish has a proper swimming ratio as an adult.

 

[Nu-Nu the eel]

Ya i guess thats what im trying to say. For example, if you told a beginner that he could have a 3" blue tang in a 30 gallon until he was 5", then he would have to give the fish away. There woul be many problems with that because of becoming attatched, not seeing the growth, etc. The chances of sucess are better if you just tell him he needs a 180 gallon for the fish and call it a day

 

[bighabeeb]

It's the holiday season, and as people get into the hobby or start looking to spend their christmas gift certificates, I've noticed an increase in threads on several forums about, "What size fish for my tank" stuff. They've been getting the usual responses, 6ft for tangs and large angels etc.

But all those threads got me thinking, why is that? I know it's supposed to be for optimal growth and to prevent stress and stunting, but in mathematical reality, it seems wrong. Hear me out for a second.

Say you have a 3 inch Blue Tang in a 72 inch tank. Now we all know that tangs are linear swimmers, they like swimming in straight lines in open water. Now say that the 72 in. tank is completely open, that Tang has a size to space ratio of 1:24, meaning that for every inch of the fish there is 24 inches of swimming room. But as the fish grows, that ratio becomes smaller and smaller. If that tang grows out to an adult size of say 10 in., then the ratio drops dramatically to approx 1:7. That's not alot of space for a swimmer that can whip through the water.

What I'm getting at here is, if 1:7 is acceptable for an 10 in. tang, why isn't it acceptable for a 3 in. tang? I know the most likely answer is stress/stunting, but if that were the case, then why wouldn't the bigger tang suffer from the same stress? Is it possible the 6ft tank rule is just being used to ensure the fish has the right space as an adult?

Excellent question - the only thing I can really guess at is that the small hippo tang knows he's going to get bigger, and that he has anticipatory stress. That having been said, I kept a baby hippo tang very successfully for 2+ years in a 72 gallon tank before moving him off to a larger tank.

A lot of it has to do with personality as well more than swimming ratios. As an example, look at yellow tangs. They're not a particularly gigantic fish, but because by their nature they swim, forage, and cover large amounts of space in the wild, you want to try to simulate the same scenario in captivity. Hence why an 8" fish (max) requires a 100 gallon + tank to be considered "happy".

Alternatively there's some fish that get quite large that can survive quite happily in smaller tanks, despite having what you refer to above as a smaller swimming ratio. Dwarf lions, for example, get to be around 7" and can survive quite happily in 45 - 55 gallons of water. Primarily because they're a generally slow/low swimming fish - as compared to the previously mentioned tangs who really like to have room to move and forage.

So in reality, I'm not sure that it has as much to do with "swimming room to size" as it does "what does this fish do out in the ocean in real life?". Plenty of people have kept tangs and similar fish in tanks far too small for them to be happy - but if what we're trying to do is simulate a small piece of the ocean then we need to reproduce the natural habitat as closely as we can. Nothing is more beautiful than watching a fish behave as it would in the wild, and that's what those tank sizes enable.

Or I could be completely full of bologna, believe as you will

 

[Krypt]

lol I believe you Mitch and I get where your coming from. I'm just one of those "why" guys that like to know why something is, not just that it's there. I think Nu-nu also hit the nail on the head, it's much easier to tell someone new to the hobby a short answer rather than a complicated ratio of sizes over time.

 

[Hondatek]

While on the topic of tank size. I don't understand why some fish need a 220 gallon which is the same footprint of a 180 just taller can't be put in a 180. It makes no sense to me at all.

 

[bighabeeb]

While on the topic of tank size. I don't understand why some fish need a 220 gallon which is the same footprint of a 180 just taller can't be put in a 180. It makes no sense to me at all.

Good question and again, the best I can figure are two scenarios:
1. Imagine a 7 foot man living in a house with 7'6" ceilings (so we're talking about tall fish there in a short tank, of course)
2. Some fish, in their natural habitat, don't stay at the same depth. They swim in open water etc - so that extra 12" of height for swimming space allows them to behave more like the way they would in the wild.

Again, that fish may do fine in the shorter tank - but if we want it to be "natural" it needs the additional space.

This is all theory, mind you - I'm relatively new to reefkeeping, though I've kept fish tank for around 10 years or so.

 

[carey]

Very good thread guys....I like looking at it from the outside so to speak. tank sizes and recommendations are ALWAYS a point of debate.

I'm also finding that the more fish I keep and the longer I have them has been opening my eyes as far as size and space. Like now I am convinced a yellow tang needs 6 feet of swim space, before having one I though maybe just maybe a 4 foot tank would do but the more I watch and see how the tang lives the more I am confident on my idea of the minimum size.

 

[Krypt]

That's what I like about this hobby. There is always debates and it creates better understanding.

 

[joy13]

I was reading an article that I found interesting Fish Stress and Disease Overview Article from FishVet, Inc. it deals with tank size but a lot of other factors.

 

[FTMMWS]

I think a lot of the minimum sizes on tanks are just BS ..Take LA for example..A few years ago they had large angels being listed as a minimum of 180 gallons,,now as of 6 months or so ago almost all are listed 250...I personally think its their way of countering the fact that a lot of people don't have 250 + tanks and when delicate angels kept dieing in 180 systems they needed to up the size..Not because they need it ,but because they had to keep refunding...I personally think "common sense" HAS to come into play ...Big fish and fish meant to grow big need big tanks

 

[austinsdad]

I can easily drive a mini and survive a long ride, but my overall happiness is increased if I was in an SUV with space to move around and do more things. In the SUV, I'm happier, in a better mood, and healthier because of my mood directly related to the space I have.

A fish not happy is a potential for illness.

Maybe my analogy doesn't work for some, but I hope you can see my point.

 

[Krypt]

I can see what your getting at Ray, but let me ask you this. Since your a full grown human, an SUV is a perfect fit for you, wouldn't it be overkill for a 2 year old? They would be happy, for sure, but they'd also be happy in a mini. That's what I was trying to come to understand. It's all about comfortable size and end game dynamics. So in the fish world, it's buying the SUV for the 2 year old because eventually he/she will need it.

 

[bighabeeb]

I can see what your getting at Ray, but let me ask you this. Since your a full grown human, an SUV is a perfect fit for you, wouldn't it be overkill for a 2 year old? They would be happy, for sure, but they'd also be happy in a mini. That's what I was trying to come to understand. It's all about comfortable size and end game dynamics. So in the fish world, it's buying the SUV for the 2 year old because eventually he/she will need it.

Ah, but what happens when the 2 year old grows up and is still able to hide under the seat when you try to remove it from the mini?

I like this analogy although the one I like better, that i've often used with folks cramming aggressive fishes into a small tank is this:
Imagine living in an airplane bathroom. Food is occasionally lobbed in to you, but you can't leave that bathroom. Every now and again the flusher breaks. Now add a very angry leprechaun into the mix (yes, I refer to damsels as angry leprechauns, just go with it). Will you survive? Well...most likely...but are you going to be happy about it? Probably not In theory, you have everything that you need to survive. Food, waste removal, and companionship (albeit undesirable companionship). Apply that to your fish.

 

[austinsdad]

Chuck, it's just that every day as I grow, I'm realizing that the small space is making me feel weird. I really don't know why. I just know that I have not much room to move and exercise my every growing 2 year old body. And I am growing, believe me! The more I can move, the more physical and mental health I have.

 

[Krypt]

Chuck, it's just that every day as I grow, I'm realizing that the small space is making me feel weird. I really don't know why. I just know that I have not much room to move and exercise my every growing 2 year old body. And I am growing, believe me! The more I can move, the more physical and mental health I have.

Excellent explanation. I think what we can conclude then (not from any scientific info, but from common sense point of view) is that the reason for the tank specs is what the fish will need if you were to keep them for the entire term of their life. The Tang in my first example will eventually need the 6ft tank so may as well start off with it.

For the people that don't start off with the correct size tank for an adult, they need to make sure they are willing to upgrade to the larger size in the future to enable the fish to live a long and healthy life.