Angels behaving strangely

[Supersalmon]

I have a heavily planted 400l tank with Co2 injection. I have noticed that my angelfish have been hanging around the surface and jerking suddenly moving about 5 cm a time in jerky movements then stopping still again. The movement would be like if someone startled you and you jumped, only they move horizontally rather than up. I stopped CO2 injection and adjusted the pump flow so that it now disturbs the surface to allow more oxygen in but so far this has made no difference. All water parameters are fine, ammonia 0, nitrite 0, and nitrate 0 (Being used up very quickly by the plants). ph is 7, I also tested the oxygen level with a commercial kit and it seemed to be good. Any ideas on this strange behaviour, they are still eating normally when i fed them this morning, could it be some kind of internal parasite

 

[WILDER]

Yes it could be a parasite, any flicking and rubbing on objects, are gills red and infalmed,white spots that they look like they have been sprinkled in salt. or gold to yellowish dusting on them, can they maintain there balance in the water, are they bloated, are scales sticking out like a pinecone.

 

[Supersalmon]

nope none of the above signs thats why it is strange, just this weird jerky motion and hanging at the top of the water, im thinking it may be an internal parasite of some sort. Maybe im just panicking over nothing. Also the temp of my tank was very high at 31C (usually kept at 28) so I added a few buckets of cold water and it has lowered to 29C but they are still doing it - very strange, its like they have a nervous twitch. Oh and all the other fish in the tank are fine. At work at the moment but will have a look see what they are at when i get home.

 

[WILDER]

Do you have an airstone for extra aeration, a twitching movement is a sign of parasites, and if your temp has shot up with the weather to fast, it can cause stress to the fish causing a parasite to attack.