Unusual Swimming

[moto]

one of my green tigers is swimming round the tank with its head down with fast movements, any ideas what it could be. all other fish are ok, my water tests are good.
ph-7.6
amonia-0
nitrite-0
nitrate-10

 

[Blitz]

It could be swimbladder. Can you discribe more about how it's swimming?

 

[moto]

It could be swimbladder. Can you discribe more about how it's swimming?

thank you for yor reply but all looks well now,he is back to normal. but he was swimming around at a steady pace not just in one place with his head pointing at the bottom of the tank, but would swim normal during feeding or when i went near the tank. i will keep an eye on them to see if it happens again and let you know, thanks again for your replying.