Originally Posted by Luke
But if i am getting a nitrate reading, doesnt that mean the right types of bacteria are present?
Maybe... but you said you never took nitrate readings beforehand, so you don't know if your nitrate was really zero to start with. A jump from 0 to 20ppm nitrates in one day seems like an awful big jump. Not sure if you're using RO
water or tap water, but if using tap water your nitrates may have been that high to start with. You could test up some stored "fresh" saltwater if you have any, and probably get a feel for what your nitrates were to start with.
Regardless... I took your comment about having the right bacteria as an indication that you thought you were good to go.
You using a floating glass hydrometer, or a swing-arm? If swing arm, then as others have said, investing in a refractometer is a really good thing.