Zebra Loaches Fighting?

[SteakNShrimp]

So I have 4 Zebra Loaches in my 55g tank and they all seemed really happy 1st week or two.

Recently, for a couple of days now, I haven’t been able to find one of them even when feeding.

Also two of the three that I do see everyday are fighting...they have just started doing this about the same time I noticed one was missing. They rub against each other and are get discolored. More brown and dirty looking than white/black. They are now back to their normal colors though and have stopped fighting...

What happened? Why are my Zebra Loaches so aggressive? Did they kill the missing one?

 

[Byron]

I've no idea about the missing loach. But the interactive behaviour you describe may well be normal social behaviour. I'm thinking it is what has been called the "loach dance," when two of the species will "grey out" (meaning, their species colour/pattern sort of fades out) as they interact. This can last for hours. They can encircle each other, reverse direction, nudge, etc. This is why loaches must be kept in groups, and five is about the minimum in most cases.