my new leo i got about 3 weeks ago is acting funny " walking " around in circles and swimming alot through out the tank... every now and then shows a quiver in his disk, no curl, checked water conditions all normal Amonia 0, nitrite 0, nitrate 20ppm, no change in ph, did a 50% water change last nite,, im woundering if my heater is causing pulses... i unplugged them hopping it helps, all other rays are fine but hiding under the sand