swimming up and down the glass

I would think they where playing but there the ones that dont get along. My water was checked and it was excellent. I can say that this is the second time that they did this, after I cleaned the inside of the glass.

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fish swimming up and down

this is called "pacing" and is most noticeable with new fish and after water changes, dont know if its true but I heard it was due to the fish wanting to be somewhere else and looking for an area more comfortable for them,maybe they like the thin film that is normally on the glass which is wiped away when you clean,I think if you notice that they do it after you clean the glass each time, then bingo, thats it! so i would re check that water first, make sure, if you dont check it yourself, that its checked for everything,and temp too,mine have done it in the past, its different to "flashing" when fish rub against rocks etc, that's down to parasites