Bioplast Bubble Counter may be one of the best for no leakage. While bubble rate is only minimally important this gives a visual indication that the CO2 is actually flowing in your system. Knowing that CO2 is going into your aquarium is very important for your plants. There are several types of counters available but this price this is definitely one you should check out. At Arizona Aquatic Gardens we aim to keep the best types of products in stock for all aquarists.