Use two of the best pumps you can find. Keep one out of the solution and use it while the other is being cleaned. No slowdown in production. Or, find a pump made from material that your solution will not plate out onto-perhaps teflon. Or use a peristaltic pump.

electroless plates more where it is agitated. It is what is called "precipitation plating", like they used to plate silver on mirrors with via slow sugar reduction. You mix it and pour it and it plates on all surfaces.

Any hotter spots or agitated spots get more metal

"Use two of the best pumps you can find" Or, two of the cheapest you can find.

Your solution means they are easy to service, either way.

Cheers!

you could use a series of air bubblers, like an aquarium, behind a solid baffle plate against one wall. The baffle plate would be 1 inch from the wall and would stop 2 inches from the bottom and 2 inches from the top. If you have an air pipe at the bottom with a tiny hole every 1/4 inch, or a row of aquarium airstones(if they will endure the conditions). The air pressure is only 1-3 PSI. As these bubbles rise they reduce the bulk density of the water and you get a vigorous circulattion. Watch out for oil in your air and the solution you bubble through must not froth.

Thanks. Since I am using a low pressure blower in the production, I will share the blower for EN agitation purpose.

Is it possible your magnetic drive pump is the problem in its self and encouraging the nickle to deposit as it is magnetic? How about a pair of large air powered piston pumps.

Also why don't you fit extension shafts on the submerged pumps and keep the motor out of the solution?

If corrosion is a problem then materials compatibility charts need to be reviewed to assess the performance of the solid at the solid/liquid interface.

Plastic pumps are made, for instance, and have solved many a problem with hydrochloric acid pumping, for example....

Just an idea:

Use a plastic shaft with a flat plate on the end like a single disk Tesla pump. Cheap easy to make. Clean it and or dispose of it. Keeps your drive motor above the tank. Flo agitation rate is set by RPM and disk diameter. If your flow must be directional make a teflon case for it.

http://www.youtube.com/watch?v=ordrp4KXEKQ This is a home made multi disk with housing. A single blade does not need the disk with holes in it.