Julienlore

I just made a DIY CO2 system (yeast fermentation) and it's now running in my 20G. I'm only using a 2L generator so nothing excessive.

I was reading some of the past threads in the forum and quite a few people were saying they avoid CO2 because it can kill fish? Is this something I should be concerned with?

Thanks,

Julien

MrWaxhead

In a DIY system the danger is that you use to much yeast in your mixture, and the mixture foams up the lines and into the tank. A single bottle in a 20g should be ample c02 unless you have very hard water. To avoid flow getting into your tank the best way is to rig another bottle between the mixture bottle and the tank. And the mixture would flow to that bottle and not the tank.

Like the followng,


Picture came from a good little site on DIY c02,
http://www.qsl.net/w2wdx/aquaria/diyco2.html

MrWaxhead

Here is a good little site on measuring your c02 in your tank.
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm

Basically test your ph and kh and enter them in the fields about half way down the page it will tell you your c02 level in your tank. You basically want about 25ppm for optimum growth. Once you get over 30ppm its harmful for your fish. I would test before your lights go out and again in the morning right before they come back on to see what levels you have, as with DIY it runs all night while your plants give off c02 as well. If you are too high in the morning you will have to add air bubbles through the night or turn up your filters to ripple the surface water to gas off c02.

If you are not getting enough c02 you can always run a second bottle like in the first post I made. Its safer that way then trying to make a stronger mix in a single bottle. One bottle with a average mix should be fine in a 20g though.
Aim for 25ppm and you should be fine and not get over 30ppm even through the night. If you do, you must add air or surface rippling at night to bleed off c02 as I mentioned earlier. Very soft water will absorb c02 much easier and faster then harder water, so if your water is soft test lots for the first few weeks to make sure everything is safe. Also if your c02 is to low, you will be more prone to algae, so as I said aim for 25ppm and you should end up with wonderful fast growing healthy plants with no algae. Also if your lighting is over 2wpg you will need a fert schedule as well. Let me know what you have for lighting over your 20g and I will help you out with a fert routine if you like.
Good luck and happy planting.

Julienlore

Thanks for all the help,

Why would the yeast get in the tank? I brew a lot of beer and wine and have never had any yeast overflow (unless I do it on purpuse with a blow off tube). If the foam (Kraeusen) doesn't reach the intake tube it won't make it's way up.

I only have 1 W per gallon but will be running a 2 W per gallon T-8 system in a few days from now.

So far I havn't fertilised any. The tank has only been running for a little under a month. Cycle only completed recently and I have added my first 3 tetras.

Thanks,

Julien

MrWaxhead

In your 2L bottle if you add to much yeast it starts to commit suicide to aggressive against the sugars, and the pressure builds up and with only one way to go its up your line and into your tank. That gas separator bottle will start to collect any scum that trys to go up the line, it also works well as a bubble counter if you fill the bottle up past the inlet tube you see in the bottle. The foam or (Kraeusen) as you mentioned is only part of what comes up if your batch is to strong the pressure can send liquid contents up as well.

But since your already have a knowledge in brewing you will already have a good understanding of mixtures, and the yeasts use for brewing especially Champagne yeast is perfect for a DIY c02 system. Its much more stable then dry active yeast. It seems to work on the sugars much slower and steadier. Dry active seems to push real hard and fast of the start and putter out quicker. Also brown sugar over white seems to work well too. I use Champagne and brown sugar and get great steady c02 runs with no foam issues ever. Also if your water is very soft, it tends to make the foam issue greater. Adding a little baking soda to your generator can help by upping the hardness in the generator and makes for way less foaming.

Personally on DIY systems, I like to run a extra bottle with lighter mixtures and splice them to a separator with one way check valves on the lines between the generators and the separator. That way I can mix my bottles at opposite times. So even when I swap one out the other is still producing while the new one comes to life. And the check valves stop o2 from enter the line to the bottle that is not being changed so it does not stop production for a bit.

Pressurized is in the end the way to go though. Its steady and gives you much more control. But on a small tank DIY can and does work fantastic. I have ran several 29g tanks with 2 generators per tank with fantastic results.

MrWaxhead

And at 2wpg you are right at the cusp of ferts. You could probably get away with weekly dose of macros, and a bi weekly dose of micros. Like seachem flourish and seachem trace.

For t8 lighting that you are going to on a 20g, I am assuming you will be using a pair of 2 foot bulbs that are 17 watts a piece, for 34 watts over 20g for 1.7wpg, but t8 are more effective watts to lumen output, they have a Efficiency lm/W rating of 1.35 so your 1.7 watts per gallon would actually be 2.295 wpg. With c02 and a few ferts your tank should be stunning and grow most plants. Might have a little trouble with some red plants or carpet plants, but should still grow them fine (just might not come into full reds, or only near the surface would full reds punch out etc). Other plants will thrive at those levels though, if you keep enough ferts and c02 to supply your plants into overdriven growth, they actually send out chemical signals in the tank that deters algae. Algae when thriving does the same thing and kills off plants. So if you get your plants thriving fast it makes it that much harder for algae to take control of your tank.