Stressed Axolotl

[Arthurs Mum]

Hi, our axolotl has been behaving very strangely. He swims against the glass and looks stressed! He has been in his new aquarium for 7weeks now. There is no ammonia, nitrate or nitrite in the water and temp is 17deg c. He is feeding well and has great colour but it's distressing to see him looking so stressed! Any help will be greatly appreciated

 

[wolfen]

are there any other signs of stress? ie.. curled gills (bent forward from base of gills) arched back, hooked tail (looks like a hook/question mark at end of tail), very red appearance (mostly applicable to albinos and leucistic), is he at surface often or frequent surface gulping?
axolotls are quite active at times although as they get older they become more active at night when it is dark and not supervised, during their activity period they will travel around to tank investigating and hunting for food, axolotl don't recognise glass and probably see it as a transparent barrier with possible food and additional places to go/swim and will travel along the glass in the hopes of getting through/around it.