Confused

[madness]

right i have a 75g tank with 10 tiger barbs in and 3 silver dollars i cycled my tank for about 5 and a half weeks and its had fish for about 6 weeks. i do weekly water changes and weekly water tests usually before a water change and ammonia and nitrites are 0 and i use the bottle water test kit not the strip version.
my problem is my tiger barbs there forever floating vertically in the water and i am under the impression that this mean the nitrites in the water are high but everytime i test for it it always comes out 0 is there anything else i could have in the water making them do this or could they be sick?

 

[*Fishkies*]

What is your nitrate reading?
Do you have a ph reading?

Does the temperature in your tank stay consistent?
Do your tiger barbs look bloated at all?

 

[Scunny]

used to have some tiger barbs and i asked the same question, apparently its normal behaviour.

 

[CruX]

Do they only do it at night? I some times catch mine doing it at night and the first time I banged the light on in panic, they seem to be fine though.