Zebra danio rubbing

[minnowbouy88]

Hi guys, occasionally one of my 5 zebra danios decides to rub himself against the filter in the tank, i researched about this and all i could find was about ich and gill flukes, none of my fish are showing any white spots at all and the only thing is only one fish does it and its not all the time so i am confused, also i am worried to treat as i am not sure what it is but also have sterbai corys in my tank also and i know they are sensitive to medications and salt, can some one please help me as i cant afford to loose any fish? Also my nitrate is still so high and i cant seem to lower could this cause it?
My tank had been fully cycled and up and running for over a year.

My tank is 120l
I have 1 internal and 1 external filter
A heater
Fish in the tank are 5 zebra danios
3 white cloud
2 sterbai cory

Water perimeters are
Ammonia 0
Nitrite 0
Nitrate .40


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[Fish king]

Are they eating ok


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[minnowbouy88]

Hi, yes all fish eating perfectly fine and are all still highly active so leaves me very confused


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[Fish king]

I can't tell you what it is but it does not seem like a illness because the others are not doing it but monitor it and if it gets worse it could be a problem if the was doing it when you got it it could just be wired Wong do to inbreeding but like I said keep an eye on it and make sure it is just that fish


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[trennamw]

How much does it do it?

Two of My danios worried me a little because I thought they were rubbing on plants but they were just playing, sort of "skipping" their bodies off things.


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[minnowbouy88]

Hi, he was doing it constantly for about an hour, I had my weekly clean yesterday and noticed a lot of sludge on top of the filter so I am starting to think he was trying to eat it as he hasn't done it since, he has been curious and been up there by the filter but not rubbed against it since it has been cleaned so hopefully I am correct. Hardest thing is these guys are so active they play from first thing in the morning to last thing at night which is always fun to watch. I shall keep you updated to any more strange behaviour


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