Silicone vs PVC tubing for dosing lines

[Bramzor]

I've been struggling with my dosing pumps on my nano tank because I need to dose only a slight amount (for example 2ml a day). Been using silicone tubing for a long time but I always had air building up in the lines and not enough fluid to clear out the bubbles so they would build up over time. Can build up enough in 24h to cause issues with dosing. Tried the smallest version of silicone tubing (1mm ID) that I could find (which helped with clearing the lines more often) but still had air in the lines, even after glueing all the connections to make sure that air cannot enter the lines through one of those.

So I made up a test where I had silicone tube dosing AllForReef, silicone tube with RO water (baseline) and a wider PVC dosing tube that I had also dosing AllForReef. My findings:

1. The silicone dosing tube with AllForReef: Had microbubbles in the silicone tube which where building up over 24h causing air pockets in the tube. Failing the test.
2. The silicone dosing tube with RO: Only had a few (3-4) microbubbles in the tube which did not cause any issues with dosing. So it did pass the test.
3. The PVC dosing tube with AllForReef: Only a few microbubbles which also did not cause any issues with dosing. To my surprise, this one passed as well.

I know silicone dosing tubes are frequently used (I even think they are more popular compared to PVC lines) but in my case, it does cause issues when dosing products like AllForReef.
Conclusion: Microbubbles are a result of a reaction between AllForReef and the silicone tube? Which I guess can happen but why isn't this a known thing? Aren't most people using silicone tubing on their dosing pumps?

 

[gbroadbridge]

I've been struggling with my dosing pumps on my nano tank because I need to dose only a slight amount (for example 2ml a day). Been using silicone tubing for a long time but I always had air building up in the lines and not enough fluid to clear out the bubbles so they would build up over time. Can build up enough in 24h to cause issues with dosing. Tried the smallest version of silicone tubing (1mm ID) that I could find (which helped with clearing the lines more often) but still had air in the lines, even after glueing all the connections to make sure that air cannot enter the lines through one of those.

So I made up a test where I had silicone tube dosing AllForReef, silicone tube with RO water (baseline) and a wider PVC dosing tube that I had also dosing AllForReef. My findings:

1. The silicone dosing tube with AllForReef: Had microbubbles in the silicone tube which where building up over 24h causing air pockets in the tube. Failing the test.
2. The silicone dosing tube with RO: Only had a few (3-4) microbubbles in the tube which did not cause any issues with dosing. So it did pass the test.
3. The PVC dosing tube with AllForReef: Only a few microbubbles which also did not cause any issues with dosing. To my surprise, this one passed as well.

I know silicone dosing tubes are frequently used (I even think they are more popular compared to PVC lines) but in my case, it does cause issues when dosing products like AllForReef.
Conclusion: Microbubbles are a result of a reaction between AllForReef and the silicone tube? Which I guess can happen but why isn't this a known thing? Aren't most people using silicone tubing on their dosing pumps?

I use Red Sea branded silicone dosing tube to dose AFR and do not see any bubbles over the last year.

Are you using a tubing designed for dosing?

 

[Bramzor]

I use Red Sea branded silicone dosing tube to dose AFR and do not see any bubbles over the last year.

Are you using a tubing designed for dosing?

Bought it online as foodgrade silicone tube. Because that was the only source for tiny ID tubing.
So maybe there are different grades of silicone tubing regarding "air permeable"

 

[Bramzor]

Replaced it with Grotech 2(ID)/4mm(OD) PVC tubing which is working great. No microbubbles anymore. I do see some larger bubbles forming after a long time but this does not seem to effect the dosing. 2 feat of tubing holds 2ml of fluid so dosing 2ml (which is exactly my dosage at the moment) will flush the lines every single day. I might even shorten the lines a bit more to lower the amount of fluid in the lines.

 

[Bramzor]

Solved: Do not get silicone dosing lines from any source, for example food grade silicone dosing line from china. Not that the dosing lines are bad, its just that silicone can allow air from getting inside the tube which causes different issues depending on what you dose.
But PVC dosing lines, always perfect (regarding "Air permeability")