I have a DIY CO2 system myself. I agree with the other posters in
that you shouldn't try and regulate yours. That can only lead to disaster!
Personally my system runs 24X7 and the Ph doesn't vary much at
night when the plants aren't processing the excess CO2 in the water
column. Your fish will be fine (truly believe that you could never
get too much CO2 in the water column with a DIY system to affect
fish).
As for your reactor, do you have a power head feeding water through
the top with the forced water exiting the bottom of the tube? If not
you are only exposing a very small surface area of water to the static
CO2. The idea with a reactor is to have the surface area and CO2 bubbles
"violently" mixing to dissolve as much CO2 into the water as possible.
You didn't mention how much lighting you have. If you want good
plant growth, and you are injecting CO2, you must have appropriate
lighting!

HTH,

DJay

"Iain Miller" wrote in message
...
"Prakash" wrote in message
...
Hi,
I've just set up my tank. 42 uk gallons, Eheim 2026 filter, sand
substrate.
The ph is 8.2 (seems to hover at 8.0 and thereabouts). Quite a few
plants
(though I can identify only the Cabomba yet), and 6 zebra danios.
I have started building a DIY CO2 system. Following questions:

1. How do I control the flow of CO2. I've put a 2 way gang valve at the
outlet of the generator, the idea being I simply throttle back to the
required level. And then I read this post about exploding DIY Co2
bottles.
Can I use the other valve on the 2 way gang to bleed excess CO2 ? I also
have a non reurn valve after the gang valve.


I'd be very careful about trying to control DIY CO2 by restricting the
flow
from the generator for the reasons you have outlined. If you are going to
try & do it then I think the way to achieve it safely would be by varying
the contents of the mixture - presumeably either use more (or less) yeast
to
try & control the rate of CO2 production. I think trying to restrict the
flow out the bottle would be a recipe for disaster - the pressure will
gradually build up and then , well, Kaboom!

OTOH. I doubt that you would be able to produce enough CO2 out of a DIY
setup (unless you used multiple generators) to cause your fish a problem.
What you could/maybe should do is to install a valve in the line that
allows
you to switch over from putting the CO2 into the tank to letting it escape
to the atmosphere. You could then use this at night.

Saying that, I suppose you could use a similar kind of arrangement to try
&
control the flow into the tank. If you had a bleed valve that would allow
very fine adjustment, you could maybe control the flow into the tank by
the
amount you let escape if you follow me. If you use std airlline fittings I
have a feeling it might be kinda on or off though! Also bear in mind that
if
you use std airline (especially the silicone variety - the soft green
stuff)
it will leak CO2 itself.

These are some of the reasons I went for a gas bottle system. See my post
yesterday about how to get your hands on cheap bottled CO2 & then maybe
look
at what you could do to build your own system. There are plenty of posts
in
google about picking up regulators & needle valves etc. The 3.5 kg bottle
that's under my tank (75 UK gallons) will last the thick end of a year I
would guess.

Not as cheap as the DIY version but less mess & hassle and less likely to
make a major mess. I know there are loads of people who use DIY but I
decided it wasn't for me!

HTH

I.