DIY CO2, water changes and Before I buy

Subject: DIY CO2 Injection
> I have already leart that DIY CO2 injection can be made from 2L 
> bottles and that the mix should be 2 cups of sugar, 1 tsp of bak
> soda and 1 tsp of yeast. I understand the bottle should be fille
> almost to the top with watter then. Besides the composition of t
> does the temperature matter much? I have some of my tanks in 
> a rather cold room - the tanks have heater though.

My living room, where the tanks I run with Yeast reactors are 
kept, is quite cool too.  I've found that I can keep my pH very 
stable by keeping the bottles sitting on a reptile tank heater.  
This is on a timer set to be one when the lights are on and off at 
night.  When the bottles cool down at night, they still put out 
some CO2, but not as much as when they're just a little warmer.

> And, is it possible
> to kill the fish by injecting too much CO2 - either by making th
> carbon dioxide replace oxygen in watter of by making the Ph drop
> much? 

Yes!!! But this is harder to do with a yeast reactor unless the 
tank is quite small.  CO2 in reasonable amounts does _not_ 
"replace" O2 in the water... quite to the contrary, tanks with the 
right amount of CO2 supplied often have O2 levels in excess of 
saturation (that's what makes those bubbles on the leaves that 
people talk about)  As far as the _amount_ of CO2 that fish will 
tolerate, it is generally accepted that a safe and effective range 
is between 15-40 mg/l.  _SOME species have been tested and found 
to tolerate levels up to 200 mg/l although this level was attained 
over a long period of time.  In the short term, pH swings seem to 
be the biggest problem with an unsteady supply of CO2.  This is 
very stressful to the fish. (probably not great for the plants 

> If so, how can I controll how much CO2 is injected with th
> setup? Finally, I understand the CO2 will make the Ph drop. Shou
> counter this by adding some baking soda to the tank water?

The best thing to do with a yeast reactor is figure out the 
"recipe" that gives you the longest steadiest supply of CO2, 
rather than LOTS of bubbles for a few days and a quick fall off.  
What works best will depend to some extent on your tap water.

A KH of 4 or higher will help keep your pH more stable.  By all 
means increase the KH if it is low in your tap water and you are 
having trouble with severe pH swings.

> From: "Robb D. VanPutte" <ROBB at bio_tamu.edu>
> Date: Wed, 14 Feb 1996 8:33:54 -0600
> Subject: Re: water changes
> Steve from breedofish at aol_com has raised an interesting question
> discussion.  I would have to agree that water in a well planted 
> to be changed as frequently as that in a tank relying only on a 
> organics.  However, it has been my understanding from reading ma
> that aquatic plants utilize ammonia as their primary N source, n
> over a few weeks time the nitrates may still build up in concnet
> probably have to severly neglect your plant tank for many weeks 
> nitrates, but it's better to be safe, right? Anyway, just my two

Actually, I have found that quite to the contrary, in my well 
planted HIGH GROWTH tanks with a moderate fish load, I _never_ see 
any measureable amounts of nitrate or phosphate, even after being 
away for several weeks on vacation when the tanks do not recieve 
regular maintenance.  There _are_ other reasons for changing water 
though ;-)


> From: Hardjono.Harjadi at Eng_Sun.COM (Hardjono Harjadi)
> Date: Wed, 14 Feb 1996 10:07:27 -0800
> Subject: Re: Before I buy ...

> [snip David Drum's list of proposed plants]

> Two of the genuses that you mentioned above are identified as ma
> the Dennerle book. They are Ophiopigon and Syngonium. The Ophiop
> sustain submersed condition for 12 months and the Syngonium can 
> submersed condition only for 2 months. The book suggested that y
> plants out of the tank and grow them emersed (half in the water,
> the water) when they were not doing well in the tank. After they
> then you can put them back in the tank.

IMO, this is a bad idea.  You are better off using plastic plants 
than using plants that cannot adapt to submerged life as 
"decorations".  Plants that are not actively growing and 
photosynthesizing are, at best, not contibuting to the health of 
the system, and are usually contributing to the waste levels in 
the tank as they break down.

Besides, if people won't stop buying these plants, suppliers have 
no incentive to stop producing them.  These are a _major_ factor 
in the people believing they "can't grow" aquatic plants... they 
are working with plant sold for aquariums that have no _hope_ of 

(I'll get down off my soap box now ;-)