Odd Dwarf Chain Loach behavior - mating or fighting?

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New Member
Mar 4, 2024
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Santa Clara, CA
2 videos
I have 9 of these awesome guys in a tall 30 gallon with 1 angel. They’ve always displayed the usual goofy playful behavior they’re known for, but tonight about 3 of them were wrestling and circling each other under the sponge filter. I also noticed they are paler than usual even though I turned the light on when I caught it happening. They didn’t seem to be hurting each other, although it looks quite aggressive. Has anyone else witnessed something like this? Are they asserting dominance or are hormones kicking in? I’m not sure how to sex them. I would say they’re about a year old, or just under (I’ve had them about 6 months). Thanks!
Did you change anything in the tank. Any changes (even just pruning) used to start mine off into a new dominance cycle. And yes the behaviour does change when they reach maturity. Mine started shredding the fins of other tank mates so I had to buy them their own tank.
Females are bigger and fatter than males who are smaller and slimmer.

Some of it looks like fighting and the very end of the first video looks like breeding.

If they don't kill each other in the next day or two, or do any physical damage, they might be breeding.

Keep filming them and you might be the first to film them breeding in captivity.
When botiid loaches go pale, it's called "greying out", they do it when stressed, or like when one is being dominated or picked on by the others, it may grey out in response. If one is constantly greyed out I'd be concerned, but they do form and re-form hiarchies within their group, and you have a good number of them, which is good! Means there's enough of them to hopefully spread out any dominating behaviour. It's nice to see someone beginning with a good number of them! :)

Behaviour definitely changes as fish mature. Anything from a store is almost certainly going to be juveniles when you buy them, then things can change a lot as they mature into adults and want to begin breeding, establishing territory, or estabishing a pecking order, depending on what kind of fish you have of course. And bottid loaches are intelligent, curious and social fish and form their own pecking orders. :) Would be great if you did manage to breed some!

@seangee keeps the same dwarf chain loaches, you can definitely trust his experiences with them. :)
Don't panic - there are unlikely to be any fatalities (at least from my experience). They do form very hierarchical societies and the alpha is invariably female - usually the biggest. I couldn't watch the videos earlier (poor reception on train) but what I saw was 2 females squabbling for supremacy. It may take a few days, or only a few hours but once the hierarchy is settled it will be accepted by all (until the next time something triggers #2 to have another go at it ;))

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