[slief]

Originally Posted by neeper

It has the older pump, model 200 VS07.

I would suggest a thorough deep cleaning. If there is friction anywhere inside the pump, that could cause the issue you are describing. The other thing it could be is if your wedge pipe is closed more than 50% you could be creating a siphon in the drain side of the skimmer. What happens is the level will rise until there is enough head pressure inside the skimmer to generate a full siphon at which point the level will suddenly drop. The fix for that is raising the sump level slightly. Maybe 1/2" and then opening the wedge pipe more or simply open the wedge pipe and see if it settles down.

For cleaning, please refer to this thread and also pay attention to post 2 in this thread discussing cleaning of the bearing since it applies to your pump. I would definitely look at the wedge pipe siphoning first but it is always a good idea to do a deep cleaning on your pumps. I recommend doing that every 4 months or so.
http://www.reefcentral.com/forums/sh....php?t=2573406