i use a rena but on a much smaller tank, 3G.

are the bubbles a fine stream coming from the side of the rena or from the
top or bottom gaskets as leaks?

make sure the rena is at the bottom of the tank for maximum effect.

also you could try a 2" since the 4" just puts the point of potential
emission higher in the tank with no benefit. i actually cut mine down to
under an inch and reassembled it.

good luck

jtm

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"Rick" wrote in message
...
I set up 2 liter bottle of DIY CO2 about 10 days ago, mixed up 2 cups of
sugar, 1/4 tsp of yeast and a pinch of baking soda and filled the bottle
about 3/4 full. I initially had this hooked into a powerhead. It was
dispensing as I could see the puffs of gas coming out of the output. I
recently bought some Rena Micro bubblers to use rather than the power head
and now have the bottle with a fresh mix (last night) hooked into a 4"
bubbler in a 20g planted tank. My Ph in the tank remains at about 7.6. I can
see bubbles coming out of the bubbler but should the PH not change ?. Is the
tank not getting enough CO2, one would think in a 20g that one two liter
bottle would be enough, yes, no??

Thx.
Rick