Not really an emergencie as such but noticed one of my Oto's with this white/red patch on hes head during tonights water change. Injury perhaps 
Any ideas Peeps

Any ideas Peeps
Hoping its nothing to serious and hes just bumped it. It looks like a burn tbf, you might be spot on there with trying to fit by the heater. They spend most the time up in the corners behind the large plants and heater.Maybe he was trying to burrow under something or fit between your heater and the glass.
Not really the barbs leave the otos and shrimp alone. All is peaceful. Must of knocked it or got too close to one of the heaters. Just going to keep a close eye on him and keep the water pristine.It looks like he bumped into something, do you have any other aggressive or semi aggressive fish in your tank?
That’s more spot on.Yeah it looks like a burn, either chemicals or from a heater
Sorry i missed this reply. Its just the 1 side. Water params are as usual. Ammonia is zero.What are your ammonia levels? The area (near the gills) looks like maybe ammonia poisoning? Is it on both sides or just the one?