Did another experiment with my sun tank. I wanted to know if I did not infuse co2 on the tank, would the Pearlweeds still produce bubbles under direct sunlight. Its been three days since I stopped giving pressurised co2 to the tank and I have observed that the Pearlweed still produces bubbles in the morning when the sunlight hits them directly and also in the afternoon even when the sunlight is not directly on them.
Don't be too happy about seeing bubbles. The reason you are still seeing bubbles is, your plants are using calcium carbonate, magnesium etc. to get their needed carbon. This method of acquiring co2 is an energy intensive means for the plants and will eventually lead to poor growth; co2 injection is not. So turn on the co2 again.