There is equel cover on both sides and i put the food in the center all the time, lighting is equel and i just suck at taking photos. Ibuilt this tank long so they had a lot of space to swim and they only use the one side for the most part.
when you feed them, gradually move the spot you dump the food each day to the left... if that makes sense... then they'll get used to the other side of the tank
I never thought about it much but mine hang out more towards the right side because I feed them there, but after they eat they move around move in the tank.
I have seen goldfish do this, usually they stay away from the side that's right against the corner(dark/boring); they could be possibly attracted to the "brighter" side of the tank. The water current didn't matter ime.