I have diy co2 system for my 29g tank.

Heres a bit of story...
Last week, I noticed that the co2 misting has decreased. Naturally I thought that one of the bottle was "dead" so I whipped up a new bottle. I should have checked the bottles before I whipped up new one... the bottles currently in use was just fine. I went ahead and swapped out one of the bottle though.

I decided to check for leak or blockages. No leaks...

Then I decided to check the airline running into the powerhead/sponge filter. I was surprised at what I found. I found this milky white thick substance completelly covered the end of airline. As I pulled the airline out of the filter, the substance came off and I heard a quite loud 'SSSSSSSSS' sound.

I actually put the substance and a piece of airline in a ziplock and put it in fridge as I wanted to look at it under microscope at school, but never gotten around to it yet.

So what is this substance? Is it a microorganism that likes co2?
How do I prevent this from happening again?

Sorry if this is a bit of read for some of you