It is true that they breath from both water and air, but they must have access to surface air or it is possible for them to drown. With that said though, I do not think that they will stay in the tubing so long that that would happen, but if they did get stuck somehow it could end badly for them.
I really like what you have done with your setup and have been looking into doing aqua bridges for some time now but have not gotten around to it. Seeing how you did yours has given me some inspiration.
Thank You Xerik for confirming what I thought was true. I do understand everyones concern about the Ploy's getting stuck. That is why I went with 3 inch PVC tubing and elbows. Now when my Poly's get bigger I will be looking into getting 4 inch or maybe 5 inch PVC to replace the 3 inch PVC. Until then I think that I am safe from any issues with stuck fish.

Sent from my GT-P5113 using MonsterAquariaNetwork App