stuff appearing on block walls

We recently bought this house, and I'm pretty sure the previous owner just painted over the cynderblock walls since there were plenty of bumps on the walls, which - when rubbed, paint came off and it looked like a white chalky substance.
Also now, I see a nastier looking substance appearing mostly at the lower foot or so of the walls - kind of a greenish brown color. I havent tried to scrape this substance yet.
We have a sump pump installed and working with piping that runs to the hole from what looks to be around the basement.
There is also a 3" cutout around the floor which I dont see any moisture in.
There was exess moisture coming in - I thought since the house had no outside drainage. So, I installed seemless gutters on it.
Question: I plan on finishing the cellar some day and I want a healthy environment. So, should I get this substance tested or something? If I've already done what I can - gutters, sump pump. Could this be being caused by outside water coming through the walls, or just excess moisture from the opening of the washer/dryer and it is condensing on the lowest part of the walls since it is colder? I had a dehumidifier running but Im waiting for recall on it.

 

fastcars,

So you got "efflorescence" which is due to soluble salts that are excreted from the cement. You might be want to brush off the "white stuff" with a stiff bristle brush and then follow by thoroughly washing the walls with clean tap water. Allow the walls to dry out to allow for any additional "white stuff" to come to the surface, which you then have to remvoe. Sure Klean 600, Diedrich 202 New Masonry Detergent can be used to do a thorough job.

Make sure the white stuff is white and not green or mustard colored which indicates mold or mildew. If it is mold or mildew, use 1-part laundry bleach, 4 parts warm water. Brush into affected areas and rinse with top water. Let it dry thoroughly.

I would recommend latex products which do include primers, sealers block fillers and finish coats; all intended for masonry surfaces. Apply one coat of masonry sealer followed with one more coat for good measure.

Hope this helps!