Ask 'Dr. Spa' Q & A Message Board

Can you tell me what kind of acid to use to test for what is going on? I seem to be having a kind of scummy bubbles floating on top of the water, not a lot, but enough to notice, when the water is filtering...I took some into a glass put it on the window sill and compared it to glassfuls of stuff I have put into the spa and thought it might be dishwasher soap residue as I wash my filters in dishwasher power in the kitchen when I change them out...but not certain...could even be swirlaway that didn't get out of the pipes at the last draining...OR, it could be organic...so please tell me the type of acid and how much I should put in a 10 ounce glass of spa water...and how much chlorine bleash (household??) to use for the same glassful of water. Thanks...