Ooooo go check your water parameters!! Heh, its the guide by which most of us live by here *grin* Seriously tho, you'll want to know if there is any measureable ammonia in the tanks; higher temps and higher pH means ammonia is more dangerous.
As for raising temps, depends on the fish. As mentioned by ferret, 78-82F is fine for Dempeys. If the temps get too high, prob the biggest sign you'll see is breathing issues, as the higher the temps the less O2
in the water. That being said, I keep my angelfish tanks at 84-86F and they have no probs.
Oh, and the higher the temps the hungrier and more active the fish. Higher temps = higher metabolism
aka Cycling Guru and the Ich Slayer
*glares at Terry and QTOFFER*
Card carrying member of FTAS & GCAS.