Do fish notice differences in tank length and width?

[Zionas]

This is something I’m curious about because I am of the probably incorrect opinion that fish need a certain number of body lengths in a tank in order to feel happy, especially for active fish. I currently believe that for a more active swimmer like an angel, tang, butterfly etc. that they need to be able to swim at least 8 times their own body length and 2.5 times their body length in the tank’s width. I might totally be overblowing this, because if a Sailfin gets to 16” (40cm) I’m sure most of you won’t say that it needs at least a 10-11 foot tank or at least 3.2m in swimming length and at least 1m in width.

However, what I’m curious about is whether fish notice if say they have 5, 10, or 20 more / less cm (2, 3 ,5 inches?) to swim around? Obviously they’ll notice the difference between a 2 foot and a 6-foot tank but what about more minute differences in dimensions?

For example, would a Blue Tang feel much happier in an 8-foot over a 7-foot tank, and notice clearly that an 8-foot allows them to swim 1 more body length?

 

[garbled]

I had a smaller blue tang for 20 years in a 6ft tank. I truly believe he would have liked a longer tank. He liked to dart very quickly in a sort of manic infinity loop path, and you could see he had to slow down at the end to make the turn, and also never really got up to full speed. (I know this, because his full speed once launched him 10 feet across the room) I think if he had more tank, he would have been a little happier when he did his manic dance every day.

In my big tank, I have a fairy wrasse that likes to do a sort of sine wave dart, where he goes down to the bottom, and then rapidly ascends, and then down, across the length of the tank. In a smaller tank, there would be a limit to the amplitude of this "wave" he does, as well as how many he can do in a pass.

Other fish I have I think don't care. It's the ones that do the high speed darts that I think notice. The ones that just meander about the tank could care less.

 

[Zionas]

Ahh from your experience which fish dart around a lot? Which ones just chill?

 

[garbled]

I think in many cases it's unique to the fish, however, blue tangs definitely. Small fairy wrasses definitely, both as stated.

I'd say stuff like cardinals, dartfish (oddly), firefish, copperband butterflies, pseudochromis, chromis, damsels, rabbitfish, clowns, dwarf angels, don't do the high speed long moves. Anthias need a bit of space to swarm and move, but they don't dart.

I also had a yellow tang, didn't dart at all. I think with tangs it's personality. The blue tang was a nervous wreck 24x7. He needed to go on rampages alot. The yellow tang just kinda slowly drifted around looking for algae or food. Same with other tangs the same body style as the yellow, mostly drifted.

All fish tend to be darty when the food goes in, so this isn't the right time to evaluate. Instead, you want to see what they do when they are just bored. If they swim fast for boredom, then they want that run distance. I highly doubt you could see this in a holding tank at the LFS.. they are just too small, so the fish can't dart at all. I suspect things that pick at rocks don't really dart. Whereas something like a blue tang is a water column feeder, so he wants to move about. In the case of the fairy wrasse, it's more of an aggression display.

Mind you I'm talking about large darts. Dartfish do dart, but it's usually on the order of 1 foot, into a hole.

 

[Zionas]

Cool. How long did your Yellow Tang live?

Keeping a fish for 20 years is darn impressive. How big was your Blue when it died?

 

[garbled]

The blue never got more than about 7 inches in length. I think I had the yellow for about 6 years.

I was *super* sad when the blue died. I mean, yeah, I had him for *so* long. I plan to get another one for my 800. I kinda hope I get another nervous wreck so I can watch him take full advantage of a 10ft span.

 

[Zionas]

Yeah, I wish I could do a 10 foot tank.

What did the Yellow die from if you don’t mind?

 

[Cole.mormon]

I wish I could do a 10 but water changes
Oh god

 

[Hugh Mann]

I've always been told that length matters more than width when it comes to the active swimmers. Just so long as there's enough room to turn around comfortably.

My little 3" hippo in a 4' tank will dash across it in a second, like a blue rocket ship.