Why do fish incessantly swim up and down against glass?

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Tanks aren't made to stimulate fish in this way. They are containment vessels. Any aspect of their construction that benefits the pets we keep are advertised as selling points. It's almost certainly a reflection and water movement response.

I've seen male bettas that will sometimes flair their gills at the glass in response to what they see as another male which is their own reflection. In cheap plastic "betta keepers" where there is no clear reflection they don't do this but when transferred to a different tank with reflective sides and no water movement I've noticed that they sometimes spend hours flaring. I've even seen people hold mirrors up to a "betta keeper" to get them to flair. Different fish react to their reflection differently. Some don't seem to react at all but swim through the currents.
 
Some fish like many species of corydoras, the males will swim up and down the inside acting like they're cleaning it to try and impress the females to induce spawning:)
 
Reflective sides? I think that's a common mistake people make. The sides are no more reflective than the front or back. Just look at the aquarium from the end rather than the front, now the front and back will appear to be reflective and you'll be able to see through the tank and to the room outside from the ends. I'm pretty sure the fish see through the glass no matter which panel it is, guess we'd have to stick our heads in a full tank and look out to verify it.

I think the appearance of reflectivity has something to do with refractive differences between water and glass when viewed at a tight angle, need someone with a better understanding of the related science than I to explain it.
 
haha that shows you how much I know. that's good stuff thank you everyone for your replies to my reply. it is curious though why they do this on the ends only. I actually don't like it. they are much more enjoyable when they are just cruising the tank.
 
Hi my fish do this from time to time,especially my cories:fish2:, now obviously one theory is the glass is reflective so stimulates the fish to show off? Also I believe its like fish are figuring out there boundaries,and as they cannot realise glass is there to withhold them within the confines of the aquarium they seem to be 'baffled'by the glass? But this wouldn't explain why mainly the side glass? But do most fish do this in corners or just on the side glass? Really need more investigation by someone cleverer than me:oops::cool:
 
My swordtails do it all the time- mostly on the north side of the tank, sometimes on the front. They'll only do it if I'm in the room, anyone else, and they'll hide with the platy.
 
friscuba said:
Reflective sides? I think that's a common mistake people make. The sides are no more reflective than the front or back. Just look at the aquarium from the end rather than the front, now the front and back will appear to be reflective and you'll be able to see through the tank and to the room outside from the ends. I'm pretty sure the fish see through the glass no matter which panel it is, guess we'd have to stick our heads in a full tank and look out to verify it.

I think the appearance of reflectivity has something to do with refractive differences between water and glass when viewed at a tight angle, need someone with a better understanding of the related science than I to explain it.

I've noticed my own reflection sometimes when I'm looking through the front of the glass if the my tank lights are dim/off and the room lights are on. So is it possible in a dim/dark room the fish can see their reflection with the tank lights on?
 
CorallineAlgae said:
I nearly choked reading that! Crazy post!

Lol its true! An adolescent dragon head to be exact, he tries to mate everything, male or female, reflection, shadow, he's not fussy. Lmao
 
shuvit said:
The reflective glass theory would explain why my male guppies try to mate with the tank sides.....horny lil critters

PMSL it's true tho cheeky guppy males I referred to them today as being like teenage boys
 
my julli corys and panda corys do that alot.especially one of my jullis which does it more often than the others.i guess they just enjoy that .they are very active lil fish:D
 
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