Firstly let me say this forum has taught me a lot of things about planted tank. My tank is just over a month old, but its good to see all flora and fauna (and the damned heebie jeebies) are doing well and happy.
Anyway, after my first failed attempt at DIYing CO2 reactor, I decided to start a new one with a new batch of yeast. (Turns out my previous yeast was probably half-staled since it was opened since about 2 yrs ago). Following the guidelines in youtube and in this forum, I managed to get the CO2 reactor up and running (waited overnight to see some bubbling action).
Then, I was stuck at DIYing the diffuser. Yep, I bought an airstone since it is cheap, but it still is giving quite BIG bubbles. Probably it's a cheapo airstone I don't know. So I proceed with trying to make myself a Bell diffuser using top side of soda bottle being cut about 4cm from the cap. It worked but when the bell is full, a HUGE BUBBLE pops up. Blegh.
So I decided to scour around my house and look for many ways to test.. finally I came to find that using my spectacles' cloth (for wiping spectacles) is a great choice to make bubbles very fine.
I run my hose direct from the CO2 reactor bottle (thru 1 check valve). Then I tied with rubber band to make a U shape. I used back the "Bell" diffuser that I made earlier and wrap the opening with the cloth. Secured it with another rubber band. And Voila it works to give 10s of tiny bubbles. I place this right under the water "return" from my filter.
And, as the saying goes, a picture worth a thousand words, there you go:
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