Heatwave oxygen worries in shrimp tank

I have a 7 gal heavily planted cube, I have a sponge filter but it doesnt create much disturbance. Not ripples just kinda 'movement'. Extra point of worry is floating plants and plants that reach the surface. Its kinda overgrown right now, like 50% of the surface is occupied

Right now im at about 2 hours until the lights go on, and of the like 12 shrimp in there I am seeing 6 or so darting around like crazy. I was thinking breeding behaviour at first but I am seeing some females darting around too. The ones that are grazing dont seem very relaxed either. They have some franticness to them. Water temp is 27,9C

Propped open the lid and using a fan to blow over the surface, for cooling and disturbing the surface a bit.

Is oxygen a big worry with these conditions? Anything else to do? no other inhabitants but bladder snails, which arent surface clustering much and are behaving quite normally.