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I have been researching and thinking about setting up one of these as one of my tanks is now planted
http://www.tropicalfishforums.co.uk/images/jlv/bigdiyco255.jpg

and I am going with the design above (except its not going to be powered). and had a question or two that I havent been able to find a answer for.

1. how do I know when the mix in the bottles has stopped working? or is it just obvious as the bubbles will stop.

2. if the 20oz bottle fills with fluid to high before the mix stopped working, is it safe to empty out the bottle or would that some how disrupt the flow?

Fish tanks are an expensive addiction

When I first setup my co2 system I checked the amount of bubbles coming out daily and left it running until it produced no more bubbles. It will take a few days to start producing bubbles and it will slow down over about a week before stopping. I change my system several days before it would slow down or after about 2weeks for me. If you are using 2 bottles you can alternate changing them and keep a more consistent co2 output than 1 bottle. For mine I've found just draining majority of the water off and refilling it with sugar and water keeps the yeast culture active so it bubbles right away instead of taking several days to get a new culture going. Currently I'm managing to keep a consistent co2 output with only 1 bottle so long as I don't wait to change it.


The 20oz bottle in the middle is usually just a backup to keep any possible yeast mixture from bubbling over. It should never fill up. In fact most of the time it won't even have anything in it. It's only there just in case something would go wrong. Sort of like the check valves. They don't do much most of the time but if the bottles were below the tank water line and your air pump quit there is a chance that without check valves the water could drain down the tubing and empty the tank. If you happen to fill the bottles too high, the mixture bubbles more than usual, or anything else goes wrong the empty bottle makes sure the mixture does not get into the tank. Creates a nasty mess if it does.

Just to throw it out there as an idea... if you've got any fish in the tank, or you've spent a fair bit on the plants, go with a tank and regulator. I've only had to adjust the valve once since i last filled my tank over 6 months ago, and that was to help clear the difuser after it some how got plugged while working on the tank. Consider the worst possibilities with a DIY system.

I am building this same system myself, if you have it up and running, Post your results please. I would be interested in reading them. I'll do likewise.

mts.gif" border="0"> I vote do you?
My Tanks at Photobucket

For DIY CO2 can't you just have two bottles going straight into the tank?

Chris

You can. The 3rd bottle is only there as a safety measure and sometimes a reactor is used to dissolve the co2 into the water more efficiently but it's not necessary. You can also run an air pump without a check valve but there is that odd occasion that if the power goes out it could create a siphon. That means water going back down the tube and the tank emptying across your floor until the water line is below where the sponge filter or airstone is sitting. In the case of airstones and wands on the bottom of the tank that could empty your entire tank killing everything and causing a nice flood. Always good to include extra safety measures when possible.

don't forget the problem of a backup from the yeast mixture. There is a possibility of the yeast mixture (a small amount) managing to get into the tank. That could prove deadly for the fish.

mts.gif" border="0"> I vote do you?
My Tanks at Photobucket