Tom I know you mention a Rio 180 in one of your posts, is that what is shown in the photo? It does not look like a Rio to me.

I am intrigued by your design and thinking of making one although I am having no problems maintaining 30-35 ppm with my diffuser. I take it with the 3/16” CO2 supply tube you don’t really need an additional bubble counter do you?

For a 55 gallon do you recommend the 4” or 6”?

Thanks
Ray