quick and dirty CO2

[Soeman]

What would be the danger of bubbling a yeast CO2 generator directly into the aquarium? I'm planning to buy/build a more sophisticated system in the near future, but I'm wondering about the danger of this setup for the time being. I've got a 30g (24"x12"x24") planted tank with fishes (1 angel, 12 cardinals, 3 khulies and 6 ottos) lit by 2 24" t12 bulbs (40W total).

My idea for the time being is to at least get a bit of CO2 into the system to help the plants until I figure out how I'm going to do the real deal. My fear is that by bubbling CO2 directly in that I'll be over dosing and asphyxiate all my fish, but I feel that without a proper CO2 diffuser that most of the CO2 will be lost.

[garnpet]

If you are using DIY CO2 don't worry about overdosing the fish, you won't be able to make it fast enough to do any damage.

A regular old CO2 ladder will do fine for a 30g tank.  You should be able to find one in most LFS or even a used one here on OVAS for cheap.

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[Soeman]

well, if DIY co2 has no worries of overdosing, I might stick with this setup longer than i'd originally intended :p I plugged the end of my airline with an airstone, and the small bubbles are almost all dissolved before reaching the surface (i have a slight downward current where I placed the airstone).

For my generator I'm using a 2L juice bottle 1/2 filled with water, and plan on adding a 2nd once I finish my next bottle of juice :p I've just got a few questions on fuel:

1a) How much sugar should I add, and 1b) how long can i expect it to last?

As I mentioned, I'll be using 2 generators, which I plan on recharging on a rotating basis. When I recharge, 2a) can I just empty 'most' of the original fuel to maintain the yeast culture, and top off with fresh water and sugar? 2b) How much should I keep?

I'm sure this info in floating around on the forum already, but after a couple hours browsing (and some getting distracted by other interesting headlines :p) I still haven't found it.

[garnpet]

There are lots of mixture suggestions available.  I used 1 teaspoon yeast, 2 cups of sugar, 1/2 teaspoon Baking Soda and 1.5L of water.  It would last anywhere from 2-4 weeks.

The yeast and sugar gets consumed during the process so there is nothing to save, when the bottle gets to low on CO2 dump all the contents and start fresh.

A word of warning!  Airstones are not the best way to get the CO2 into the tank.  If they get clogged it is surprising how much pressure can build up in the bottle and when it lets go it can be a real mess.

[Soeman]

i'll keep that word of warning in mind... perhaps i'll devise a pressure release valve (something like a wine making airlock would be simple enough to retro fit).

Yeast however, does not get consumed. Yeast is a single celled fungi that multiplies. They can die in their own 'excrements' (alcohol), or die of starvation if all the sugar is consumed, but if even so much as 1 cell survives the population will rebound given the right conditions.

However, most sites i read tend to agree with you and suggest restarting from scratch... is this due to low yeast survivorship by the end of 2 weeks, or more for the purposes of getting rid of all the alcohol content? both?

Yeast is not expensive, but why spend it at-all when you've got a perfectly healthy culture in your CO2 generator?

[fischkopp]

What would be the danger of bubbling a yeast CO2 generator directly into the aquarium?

I want to mention two things here:

1. Bubbling the CO2 directly into the aquarium doesn't cause any harm, but you will be wasting lots of CO2: as soon as the bubble gets to the surface, it's lost. CO2 reactors or ladders like garnpet suggested are build to maximize the time the CO2 gets in contact with the water, so that more gets eventually dissolved. Ideally, you don't want to see any bubbles reaching the surface at all.

2. Creating DIY CO2 is an uncontrolled reaction. Being to generous with sugar and east combined with warm ambient temperature can generate A LOT of CO2 at once. I have seen my fish gasping on the surface before after refilling my DIY CO2. So be cautious, follow the various recipes you can find in the web and don't overdo it ... at least until you know what the outcome will be.

As always if you play with CO2: stick around for the day so you can react quickly in case something goes wrong.