I agree with CAM78, when I was using a plastic hydometer it said my sg was at 1.025 and the refractometer said it was 1.031 so double check with a refratometer if you can before raising too much, can you have your water tested at a fish store? Your testing said the nitrite was at .25, have you checked ammonia, there should be no nitrite but it may be a bad reading, how long has your tank been set up?