I did a bit of a sesarch and found that these are rated to be enough for a 150 litre tank. My own experiences are with Rena air pumps and some older ones long ago. What I have found with the Rena is that they have 2 ratings. The first tells you how many typical air stones hte pump can supply at different water depths and is how I selected mine. The second rating talks about how big a tank it is meant to supply. In my case, I bought one based on the number of air stones I wanted to run and how deep my tank was. The particular model also said on the box that it was suitable for tanks up to 40 or 50 gallons. It is working fine on a 120 gallon tank and has been doing so non-stop for 4 years. When I wanted one to run a 29 gallon and a 20 gallon, I again looked at the air flow ratings and decided on one that was rated for about a 20 gallon tank. It also has plenty of power for my uses and has been a reliable air pump. If this trend carries over to the Tetratec brand, it should be more than enough for decorative bubbles in a bit larger tank than the rating on the box.