BBA means not enough CO2. Check what you have in the water by taking a tank sample, letting it sit in a shallow glass overnight, check the PH and compare it to the PH of the water in the tank after CO2 is on for a couple of hours. The tank water should be about 1.0 PH units lower, but no more than 1.1 lower (1.3 lower means double the CO2 that 1.0 means). I aim at .8 to 1.1. The accuracy of measuring the PH isn't good enough to make this a perfect measurement, but it beats the PH/KH method, which overestimates the ppm of CO2 if your water is off someway.