Fish Swimming Space Requirements?

[JHemdal]

All,

I've been working on a project that would help quantify the swimming space actually needed for "open water swimmers" in captivity. There are a huge number of variables, but it seems that this is something that can be "ballparked" without too much difficulty.

I would like folks to help me run some real aquariums through the process to see if it works. As a public aquarium curator, I can't really use my own exhibits, because the volumes are too large, and the results would not apply to regular home aquariums.

Here is the set-up:

1) Please, do not be critical of the model until I've tested it. Opinions about tank size should be posted in the original thread "Calling out the tang police" in the Reef Fishes forum.

2) First; calculate the open water volume of your aquarium in gallons. To do this, measure the water in front of any live rock/coral in inches, length x width x height and divide by 231. This gives that volume in gallons. Please do not use your aquarium's rated volume unless it is completely open water with no obstructing decorations.

3) Select the fish to use. They need to be open water swimmers, so tangs, parrotfish, pterocaesio, wrasses, anything that is mostly "on the move". Angelfish might be borderline, Anthias, Pseudochromis and the like won't work. Measure the fish's total length in inches, round off to the nearest half inch.
NOTE: the fish must be in good condition, and have been in the aquarium for at least six months!

4) Divide the gallons of open water by the length of each fish, and put a "1:" in front of it to produce a ratio. Round off to one decimal place. Do this for each fish.

5) Post your results here. I really appreciate it!


Example:


A 55 gallon aquarium that has a 10" long pile of live rock in one corner, and has an open water measurement of 38" x 12" x 12" = 5472 divided by 231 = 23.7 gallons of open water.

3" coris wrasse 23.7/3 = 1:7.9
2" hepatus tang 23.7/2 = 1:11.9
4.5" kole tang 23.7/4 = 1:5.3



Thanks!

Jay Hemdal

 

[BeanAnimal]

Greetings Jay.

I understand the math and the model, but am not sure how it is going to correlate to a space requirement. Could you explain more?

 

[JHemdal]

BeanAnimal,

I'd really prefer to collect data at this point as opposed to discussing the relative merits of the model. But, if you aren't clear about it, others won't be either, so here is some more information:


I'm working on a couple of magazine articles, one on hepatus tangs and one on swimming space required for fish. I would like people to help with this if they are so inclined, by suplying me with data regarding their properly operating home aquariums. I do not have acess to this sort of data myself, as I mentioned.

Home aquarists - especially neophytes, need a simple tool to let them know if they are about to put a fish in an aquarium that would be too small for it in terms of swimming space. Most aquariums hit their territorial limit long before they reach a biological limit (Hemdal 2006). And most open water swimmers require space based on their lengths, and not their mass (i.e. tangs and Pterocaesio of the same length need about the same space, despite their vastly different masses). For sedentary fish such as anglers, there is no need to model this.
One problem would be the Scarids. As has been pointed out many times, these fish lack the turning ability that most Acanthurids have, and they actually may require more open water.

Still, it seems to me that a trend is showing up where problems with swimming room are simply not seen at certain ratios and above.

So again, please - I need data to test the model right now, if the data doesn't fit using real world examples, then I'll change the model.


Jay

 

[billsreef]

Interesting concept. I'll try and remember to take a few measurements of my tanks and tangs at home for you later tonight.

 

[91yota]

my current setup:

75g perfecto with corner overflow... approx. 35% filled with rock/coral

75g x 65% = 48.75g of open, unobstructed swimming space

in this i have 1 four inch yellow tang (Z. flavascens)

48.75g/4" = 12.2

therefore the ratio for this fish in this aquarium is 1:12.2

i believe that this tang, being the only tang in the system, can live a very comfortable life up to around 7-8" (at which point the ratio would be 1:6.1)...

this fish shows no signs of stress, does not pace but rather casually cruises along picking at the LR...

 

[BeanAnimal]

<a href=showthread.php?s=&postid=13995147#post13995147 target=_blank>Originally posted</a> by billsreef
Interesting concept. I'll try and remember to take a few measurements of my tanks and tangs at home for you later tonight.

What he said...

 

[El-ahrairah]

Zebrasoma xanthurum... 6+ years very healthy, eventually 5 inches in length in a 75 gallon with roughly 45 gallons swimming space... 1:9 ratio.
-Michael

 

[Sarcophyton69]

Jay

My current set-up is standard 75. I have approx. 75% swim room

7 inch Regal 1:8 had for 6.6 Years
4 inch Scopas Tang 1:14 had for 6.4 years
4 inch Tolini Tang 1:14 had for 2.8 years
2 inch Starki Damsel 1:28 had for 1.2 years

 

[landlord]

Jay,

I want to play but I want to be accurate as well. You wouldn't happened to have some sort of calculation "rough one at best" to help determine the amount of water displaced by liverock. Like 8 lbs of liverock displaces 1 gallon of water. Understandibly this will vary based on the density of the rock but any thoughts. I got a 90 gal with 150 lbs.....

Kurt

 

[JHemdal]

Kurt,

I was thinking more of just measuring the open water space in the aquarium and multiplying that by length / width / height and divide by 231.
While I like your thought about calculating displacement of the live rock (Since most aquarists pay dearly for it, they usually know how many pounds they bought) the problem is that the interstices between the rocks would actually add to the tank's "volume" yet would not be too available for use by open water swimmers. For example, we built a 1300 gallon reef that uses stacks of milk crates to hold up a thin veneer of live rock. There is plenty of "void space" back there, but since the open water swimmers don't use it, I didn't want to add it to this particular calculation.

So: I think that most aquarists stack their live rock in one mass, usually along the back wall of the tank. What Im proposing then, is that you take a tape measure outside the tank, and just estimate the volume of the open water in front of the rock - the area where most of the fish swim.

Thanks all to everyone who has helped so far - do you see the same trend that I do? Most aquarists are giving their fish ratios of at least 1:6, usually 1:8 or much more.

Please - keep the data coming!


Jay

 

[landlord]

10-4

Let's see

90 gallon approx 60% free = 54 gallons

Zebrasoma flavescens (3in) = 1:18
Centropyge bicolor (4in) = 1:13.5
Valenciennea puellaris (4in) = 1:13.5
Doryrhamphus pessuliferus (5in) = 1:10.8
Pseudanthias bartlettorum x2 (3.5in) = 2x 1:15.4
Cirrhilabrus lubbocki (3in) = 1:18
Halichoeres chloropterus (3in) = 1:18
Amphiprion frenatus x2 (4in, 2in) = 1:13.5, 1:27

 

[JHemdal]

Thanks Kurt,

And your post brings up another issue, one that I intend to address later on - your 5" pipefish obviously would not need the same space as a 5" tang. Same with moray eels. I think that once I've collected enough ratios, the next step would be to categorize common species of fish into relative need for swimming room, and then assign a minimum ratio for each type.
Perhaps five categories with parrotfish in 5 and anglerfish in 1.

Jay

 

[JHemdal]

And a New Year's "Bump" for this thread!

Thanks,

Jay

 

[JHemdal]

All,

I was working on this project yesterday and thought I'd try out the whale sharks at the Georgia Aquarium to see what their ratio was. I know that their Ocean Explorer tank is 6.3 million gallons. One of their previous sharks had measured 22'. So I worked out the inches of fish to gallons of water ratio for that and it came to:

1:23,885

Now with that tank and some people's concerns that it might not be large enough for a full grown whale shark, you'd think the ratio would be below 1:12, and yet it is orders of magnitude in the other direction.

So - the model apparently doesn't work for large tanks - why not? Does anyone have the math background to tell me?

If you work out the ratio using just the tank's length of 284', you come up with a ratio of 1:13 - right where I would expect it.

I think when using a ratio of the LENGTH of the fish to the VOLUME of the aquarium, the ratio changes drastically in big tanks because as the fish's length increases linearly, the volume goes up by the cube.

Can anyone think of a solution to this?


Jay