I had a pf-300 on my 20l for about a year I had it lose siphon one time but that's because the u-pipe cracked down the seam... So if I were u I would add a second u-pipe just incase
They work great. Only thing is be careful on your flow. I purchased the pf1200 thinking bigger is better but in this case I is not as only one tube out of the two will stay running as the flow is not enough and bubbles form at the top causing it to eventually stop flowing with a fx6. Not that big of deal just could have went with a cheaper one.