I usually just take my dockside water hose down into the bilge and wash it down with the high pressure nozzle. Do that on a regular basis and you won't need to use any cleaners, but if you do, any decent cleaner will do. Simple Green, Fantastic, Spray 9, etc. Just put some cleaner in the sump tank and hit it with the hose. The water will pump itself out.
You want to keep that sump tank fairly clean so crud doesn't build up and it won't start to stink.