RE:DIY CO2 Reactor

> Malaysia
> I am looking for advise to improve my DIY CO2 Reactor gas output for my
> 40 gallon tank.
> I use a 2 liter soda bottle for my CO2 reactor and mix 2 cups of sugar
> and 1/4 teaspoon of yeast and water filled up to 2" below the cap cover,
> so far the CO2 generated is only about 2 ~3 bubbles per minute
> .... Is this sufficient ?


For my experience,no.
You shold see after 1 day workink 1-2 bubbles per second.
I think you may have lekeage on bottle cup or on some part of CO2 line to tank.

> 1. How can I increase the rate of CO2 output and what is the normal
>    rate of CO2 generated from this type of DIY system ?

Rate of CO2 may be encreased adding more yeast, but as you have done 
isn't necessary. 
You could buffer water adding 1 tsp of baking soda.

My yeast is bubbling from 15 days at a rate of 1 bubble/second with same 
your ratio sugar/yeast/soda, and for my 50g tank is more than sufficient.
Last night had to add a stone blowing air because some babies Siamenses
added were grasping for oxigen. Furthermore PH was 6 and I would prefere
to be 6.5.

> 2. I also experience very low CO2 release pressure into the tank when I place
>    the soda bottle higher than the water level of the tank. Where should the
>    soda bottle be placed to get a reasonable gas release pressure into the tank.

Again check for a failure. May you try with soped water to control on bottle cup.
I use a 5 liter canister (in Italy used to buy demineralized water) with screwed
tap. I drilled it than siliconed a connecting tube (L shaped).
Lurching, someone suggested also to put a bit of vaseline on thread, my be good
My canister is at level floor inside the tank stand, about 120 cm lower
the water level, and becomes a little "round" for the generated pressure.
> 3. What are the methods use to connecting the CO2 line into the tank ?
>    .... to diffuser, or power head ?

My last system is to spry directly into tank from outlet of powerhead.
Previous was to bubble under a DIY bell but I was not happy to see the bell.

Actually the end pipe of water is at middle of tank and I have applied
a Fluval venturi normally used as air intake for oxigen bubbles.
As told it is working wonderfully till now and I hope in future. 
Don't forget to apply to CO2 line a unidirectional valve to avoid disasters...
The CO2 thus is also helped to bubble by the depression made from venturi !

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