Silly question, do you mean you bought the pump in the link, or this one https://www.eheim.com/en_GB/products/technology/air-pumps/air-pump-200 The reason I ask is because the one in your link doesn't have a 200 model, and is for pumping water not air!
The pump in my link is the one I have, only the 100 as it's only for a 26 litre tank. I would get a one way valve, they are pretty cheap on Ebay. I managed to break the one that came with my first pump as the tubing kept coming off and I was a bit heavy handed pushing it back on one day. I bought a pack of 2 new ones, but I'm still using the first. Make sure you fit them the right way round.
It is not a good idea to keep the lights on 24/7. Fish need a period of total darkness every 24 hours.
The pump in my link is the one I have, only the 100 as it's only for a 26 litre tank. I would get a one way valve, they are pretty cheap on Ebay. I managed to break the one that came with my first pump as the tubing kept coming off and I was a bit heavy handed pushing it back on one day. I bought a pack of 2 new ones, but I'm still using the first. Make sure you fit them the right way round.
It is not a good idea to keep the lights on 24/7. Fish need a period of total darkness every 24 hours.