?A small thing can make a big difference. Buy a bubble counter for your beloved fish tank. Why not try thisWYIN W00-02A Single-head Aluminum Alloy &amp; Glass Fish Tank Bubble Counter with Non-return Function Silver? As long as you have it， you can clearly know the volume of carbon-dioxide through the rising air bubbles from the bottom， so as to regulate the carbon-dioxide supply for plants in the fish tank. It has a non-return function to prevent the backflow when the pressure changes. Made of tough material， it is durable for long-term use.                                    Features             High quality and low price<br> Small and compact<br> Easy to install and replace<br> A non-return function to prevent the backflow when the pressure changes<br> Made of tough material for long-term use   <br>                                                            Specifications            Material    Aluminium Alloy &amp; Acrylic    <br>Color    Silver    <br>Brand    WYIN    <br>Model    W00-02A    <br>Dimensions    (3.27 x 0.87)" / (8.3 x 2.2)cm (L x Dia.)    <br>Weight    1.06oz / 30g     <br>                                                            Package Includes            1 x Bubble Counter<br>