Help With Electromagnetic Shielding, Please?

Take things in order.

First eliminate mechanical vibration. Use something like soft rubber weatherstripping to mount the pumps. Or just hold the pump in your hand momentarily to see.

Second eliminate line surges caused by parallel running fields. Two wires that run parallel for any distance can cause some distortion.
Use separated power sources, or co-axial cable for a lead. Auto techs call it sympathetic crossfire and it used to put holes in pistons.

To learn more about your problem try locking the magnets mechanically while motor spins. Don't do it too long though. This may not be possible with your pump

If it's electromagnetic pulses a grounded piece of aluminum foil or a suppressor on the motor should do it.

If it is magnetic pulses then I would move the pumps, and use some sort of plumbing arrangement to get the job done. Alternatively try a peice of stainless steel sheet metal to dampen the pulses.

Radio Shack has many different varieties of noise suppression capacitors used in suppressing engine noise in auto sound systems if it looks appropriate.

MechSmith is probably right. I have definately had the image bounce around from mechanical vibration. In my case, better physical support of the monitor was the solution.

Being that there is no discoloration on your screen I would bet that the problem isn't with the proximity of the pump to the monitor itself but is with the proximity of the wires to/from your monitor or from feedback through the power source.

Isolate the pump from the electrical circuit your PC/Monitor are plugged into so that it is on a seperate circuit breaker and keep all of the aquarium's electrical lines as far as possible from your PC's electrical lines - especially the low voltage signal lines!

You sure it's the pump? Settings on the monitor itself can cause the vibration.

Thanks for the ideas people! I've come up with a solution, but it doesn't really diagnose the problem precisely. I moved the pump to the other side of the tank and ran a small pipe from it's output over to where I want the flow.

In this pump it's the magnet/s that move. I would imagine the pump's casing contains the power coils, which are completely sealed inside and out. There is a cylindrical cavity inside the casing (thus the inside and out mentioned above) with a small metal rod sticking straight up from the center. The magnet, with an impeller attached, slips over this rod. Then the impeller cover and output fixture are snapped into place. -It must have a little bit of wobble to it.

Thanks again!